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<h1>Node.js v18.19.1 documentation</h1>
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Table of contents
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<div class="picker"><div class="toc"><ul>
<li><a href="#web-streams-api">Web Streams API</a><ul>
<li><a href="#overview">Overview</a><ul>
<li><a href="#example-readablestream">Example <code>ReadableStream</code></a></li>
</ul>
</li>
<li><a href="#api">API</a><ul>
<li><a href="#class-readablestream">Class: <code>ReadableStream</code></a><ul>
<li><a href="#new-readablestreamunderlyingsource--strategy"><code>new ReadableStream([underlyingSource [, strategy]])</code></a></li>
<li><a href="#readablestreamlocked"><code>readableStream.locked</code></a></li>
<li><a href="#readablestreamcancelreason"><code>readableStream.cancel([reason])</code></a></li>
<li><a href="#readablestreamgetreaderoptions"><code>readableStream.getReader([options])</code></a></li>
<li><a href="#readablestreampipethroughtransform-options"><code>readableStream.pipeThrough(transform[, options])</code></a></li>
<li><a href="#readablestreampipetodestination-options"><code>readableStream.pipeTo(destination[, options])</code></a></li>
<li><a href="#readablestreamtee"><code>readableStream.tee()</code></a></li>
<li><a href="#readablestreamvaluesoptions"><code>readableStream.values([options])</code></a></li>
<li><a href="#async-iteration">Async Iteration</a></li>
<li><a href="#transferring-with-postmessage">Transferring with <code>postMessage()</code></a></li>
</ul>
</li>
<li><a href="#class-readablestreamdefaultreader">Class: <code>ReadableStreamDefaultReader</code></a><ul>
<li><a href="#new-readablestreamdefaultreaderstream"><code>new ReadableStreamDefaultReader(stream)</code></a></li>
<li><a href="#readablestreamdefaultreadercancelreason"><code>readableStreamDefaultReader.cancel([reason])</code></a></li>
<li><a href="#readablestreamdefaultreaderclosed"><code>readableStreamDefaultReader.closed</code></a></li>
<li><a href="#readablestreamdefaultreaderread"><code>readableStreamDefaultReader.read()</code></a></li>
<li><a href="#readablestreamdefaultreaderreleaselock"><code>readableStreamDefaultReader.releaseLock()</code></a></li>
</ul>
</li>
<li><a href="#class-readablestreambyobreader">Class: <code>ReadableStreamBYOBReader</code></a><ul>
<li><a href="#new-readablestreambyobreaderstream"><code>new ReadableStreamBYOBReader(stream)</code></a></li>
<li><a href="#readablestreambyobreadercancelreason"><code>readableStreamBYOBReader.cancel([reason])</code></a></li>
<li><a href="#readablestreambyobreaderclosed"><code>readableStreamBYOBReader.closed</code></a></li>
<li><a href="#readablestreambyobreaderreadview"><code>readableStreamBYOBReader.read(view)</code></a></li>
<li><a href="#readablestreambyobreaderreleaselock"><code>readableStreamBYOBReader.releaseLock()</code></a></li>
</ul>
</li>
<li><a href="#class-readablestreamdefaultcontroller">Class: <code>ReadableStreamDefaultController</code></a><ul>
<li><a href="#readablestreamdefaultcontrollerclose"><code>readableStreamDefaultController.close()</code></a></li>
<li><a href="#readablestreamdefaultcontrollerdesiredsize"><code>readableStreamDefaultController.desiredSize</code></a></li>
<li><a href="#readablestreamdefaultcontrollerenqueuechunk"><code>readableStreamDefaultController.enqueue([chunk])</code></a></li>
<li><a href="#readablestreamdefaultcontrollererrorerror"><code>readableStreamDefaultController.error([error])</code></a></li>
</ul>
</li>
<li><a href="#class-readablebytestreamcontroller">Class: <code>ReadableByteStreamController</code></a><ul>
<li><a href="#readablebytestreamcontrollerbyobrequest"><code>readableByteStreamController.byobRequest</code></a></li>
<li><a href="#readablebytestreamcontrollerclose"><code>readableByteStreamController.close()</code></a></li>
<li><a href="#readablebytestreamcontrollerdesiredsize"><code>readableByteStreamController.desiredSize</code></a></li>
<li><a href="#readablebytestreamcontrollerenqueuechunk"><code>readableByteStreamController.enqueue(chunk)</code></a></li>
<li><a href="#readablebytestreamcontrollererrorerror"><code>readableByteStreamController.error([error])</code></a></li>
</ul>
</li>
<li><a href="#class-readablestreambyobrequest">Class: <code>ReadableStreamBYOBRequest</code></a><ul>
<li><a href="#readablestreambyobrequestrespondbyteswritten"><code>readableStreamBYOBRequest.respond(bytesWritten)</code></a></li>
<li><a href="#readablestreambyobrequestrespondwithnewviewview"><code>readableStreamBYOBRequest.respondWithNewView(view)</code></a></li>
<li><a href="#readablestreambyobrequestview"><code>readableStreamBYOBRequest.view</code></a></li>
</ul>
</li>
<li><a href="#class-writablestream">Class: <code>WritableStream</code></a><ul>
<li><a href="#new-writablestreamunderlyingsink-strategy"><code>new WritableStream([underlyingSink[, strategy]])</code></a></li>
<li><a href="#writablestreamabortreason"><code>writableStream.abort([reason])</code></a></li>
<li><a href="#writablestreamclose"><code>writableStream.close()</code></a></li>
<li><a href="#writablestreamgetwriter"><code>writableStream.getWriter()</code></a></li>
<li><a href="#writablestreamlocked"><code>writableStream.locked</code></a></li>
<li><a href="#transferring-with-postmessage_1">Transferring with postMessage()</a></li>
</ul>
</li>
<li><a href="#class-writablestreamdefaultwriter">Class: <code>WritableStreamDefaultWriter</code></a><ul>
<li><a href="#new-writablestreamdefaultwriterstream"><code>new WritableStreamDefaultWriter(stream)</code></a></li>
<li><a href="#writablestreamdefaultwriterabortreason"><code>writableStreamDefaultWriter.abort([reason])</code></a></li>
<li><a href="#writablestreamdefaultwriterclose"><code>writableStreamDefaultWriter.close()</code></a></li>
<li><a href="#writablestreamdefaultwriterclosed"><code>writableStreamDefaultWriter.closed</code></a></li>
<li><a href="#writablestreamdefaultwriterdesiredsize"><code>writableStreamDefaultWriter.desiredSize</code></a></li>
<li><a href="#writablestreamdefaultwriterready"><code>writableStreamDefaultWriter.ready</code></a></li>
<li><a href="#writablestreamdefaultwriterreleaselock"><code>writableStreamDefaultWriter.releaseLock()</code></a></li>
<li><a href="#writablestreamdefaultwriterwritechunk"><code>writableStreamDefaultWriter.write([chunk])</code></a></li>
</ul>
</li>
<li><a href="#class-writablestreamdefaultcontroller">Class: <code>WritableStreamDefaultController</code></a><ul>
<li><a href="#writablestreamdefaultcontrollererrorerror"><code>writableStreamDefaultController.error([error])</code></a></li>
<li><a href="#writablestreamdefaultcontrollersignal"><code>writableStreamDefaultController.signal</code></a></li>
</ul>
</li>
<li><a href="#class-transformstream">Class: <code>TransformStream</code></a><ul>
<li><a href="#new-transformstreamtransformer-writablestrategy-readablestrategy"><code>new TransformStream([transformer[, writableStrategy[, readableStrategy]]])</code></a></li>
<li><a href="#transformstreamreadable"><code>transformStream.readable</code></a></li>
<li><a href="#transformstreamwritable"><code>transformStream.writable</code></a></li>
<li><a href="#transferring-with-postmessage_2">Transferring with postMessage()</a></li>
</ul>
</li>
<li><a href="#class-transformstreamdefaultcontroller">Class: <code>TransformStreamDefaultController</code></a><ul>
<li><a href="#transformstreamdefaultcontrollerdesiredsize"><code>transformStreamDefaultController.desiredSize</code></a></li>
<li><a href="#transformstreamdefaultcontrollerenqueuechunk"><code>transformStreamDefaultController.enqueue([chunk])</code></a></li>
<li><a href="#transformstreamdefaultcontrollererrorreason"><code>transformStreamDefaultController.error([reason])</code></a></li>
<li><a href="#transformstreamdefaultcontrollerterminate"><code>transformStreamDefaultController.terminate()</code></a></li>
</ul>
</li>
<li><a href="#class-bytelengthqueuingstrategy">Class: <code>ByteLengthQueuingStrategy</code></a><ul>
<li><a href="#new-bytelengthqueuingstrategyinit"><code>new ByteLengthQueuingStrategy(init)</code></a></li>
<li><a href="#bytelengthqueuingstrategyhighwatermark"><code>byteLengthQueuingStrategy.highWaterMark</code></a></li>
<li><a href="#bytelengthqueuingstrategysize"><code>byteLengthQueuingStrategy.size</code></a></li>
</ul>
</li>
<li><a href="#class-countqueuingstrategy">Class: <code>CountQueuingStrategy</code></a><ul>
<li><a href="#new-countqueuingstrategyinit"><code>new CountQueuingStrategy(init)</code></a></li>
<li><a href="#countqueuingstrategyhighwatermark"><code>countQueuingStrategy.highWaterMark</code></a></li>
<li><a href="#countqueuingstrategysize"><code>countQueuingStrategy.size</code></a></li>
</ul>
</li>
<li><a href="#class-textencoderstream">Class: <code>TextEncoderStream</code></a><ul>
<li><a href="#new-textencoderstream"><code>new TextEncoderStream()</code></a></li>
<li><a href="#textencoderstreamencoding"><code>textEncoderStream.encoding</code></a></li>
<li><a href="#textencoderstreamreadable"><code>textEncoderStream.readable</code></a></li>
<li><a href="#textencoderstreamwritable"><code>textEncoderStream.writable</code></a></li>
</ul>
</li>
<li><a href="#class-textdecoderstream">Class: <code>TextDecoderStream</code></a><ul>
<li><a href="#new-textdecoderstreamencoding-options"><code>new TextDecoderStream([encoding[, options]])</code></a></li>
<li><a href="#textdecoderstreamencoding"><code>textDecoderStream.encoding</code></a></li>
<li><a href="#textdecoderstreamfatal"><code>textDecoderStream.fatal</code></a></li>
<li><a href="#textdecoderstreamignorebom"><code>textDecoderStream.ignoreBOM</code></a></li>
<li><a href="#textdecoderstreamreadable"><code>textDecoderStream.readable</code></a></li>
<li><a href="#textdecoderstreamwritable"><code>textDecoderStream.writable</code></a></li>
</ul>
</li>
<li><a href="#class-compressionstream">Class: <code>CompressionStream</code></a><ul>
<li><a href="#new-compressionstreamformat"><code>new CompressionStream(format)</code></a></li>
<li><a href="#compressionstreamreadable"><code>compressionStream.readable</code></a></li>
<li><a href="#compressionstreamwritable"><code>compressionStream.writable</code></a></li>
</ul>
</li>
<li><a href="#class-decompressionstream">Class: <code>DecompressionStream</code></a><ul>
<li><a href="#new-decompressionstreamformat"><code>new DecompressionStream(format)</code></a></li>
<li><a href="#decompressionstreamreadable"><code>decompressionStream.readable</code></a></li>
<li><a href="#decompressionstreamwritable"><code>decompressionStream.writable</code></a></li>
</ul>
</li>
<li><a href="#utility-consumers">Utility Consumers</a><ul>
<li><a href="#streamconsumersarraybufferstream"><code>streamConsumers.arrayBuffer(stream)</code></a></li>
<li><a href="#streamconsumersblobstream"><code>streamConsumers.blob(stream)</code></a></li>
<li><a href="#streamconsumersbufferstream"><code>streamConsumers.buffer(stream)</code></a></li>
<li><a href="#streamconsumersjsonstream"><code>streamConsumers.json(stream)</code></a></li>
<li><a href="#streamconsumerstextstream"><code>streamConsumers.text(stream)</code></a></li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
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<li><a href="webcrypto.html" class="nav-webcrypto">Web Crypto API</a></li>
<li><a href="webstreams.html" class="nav-webstreams active">Web Streams API</a></li>
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<span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span>
Other versions
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<div class="picker"><ol id="alt-docs"><li><a href="https://nodejs.org/docs/latest-v18.x/api/webstreams.html">18.x <b>LTS</b></a></li>
<li><a href="https://nodejs.org/docs/latest-v17.x/api/webstreams.html">17.x</a></li>
<li><a href="https://nodejs.org/docs/latest-v16.x/api/webstreams.html">16.x <b>LTS</b></a></li></ol></div>
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Options
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<a href="all.html">View on single page</a>
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<a href="webstreams.json">View as JSON</a>
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<hr>
</header>
<details id="toc" open><summary>Table of contents</summary><ul>
<li><a href="#web-streams-api">Web Streams API</a><ul>
<li><a href="#overview">Overview</a><ul>
<li><a href="#example-readablestream">Example <code>ReadableStream</code></a></li>
</ul>
</li>
<li><a href="#api">API</a><ul>
<li><a href="#class-readablestream">Class: <code>ReadableStream</code></a><ul>
<li><a href="#new-readablestreamunderlyingsource--strategy"><code>new ReadableStream([underlyingSource [, strategy]])</code></a></li>
<li><a href="#readablestreamlocked"><code>readableStream.locked</code></a></li>
<li><a href="#readablestreamcancelreason"><code>readableStream.cancel([reason])</code></a></li>
<li><a href="#readablestreamgetreaderoptions"><code>readableStream.getReader([options])</code></a></li>
<li><a href="#readablestreampipethroughtransform-options"><code>readableStream.pipeThrough(transform[, options])</code></a></li>
<li><a href="#readablestreampipetodestination-options"><code>readableStream.pipeTo(destination[, options])</code></a></li>
<li><a href="#readablestreamtee"><code>readableStream.tee()</code></a></li>
<li><a href="#readablestreamvaluesoptions"><code>readableStream.values([options])</code></a></li>
<li><a href="#async-iteration">Async Iteration</a></li>
<li><a href="#transferring-with-postmessage">Transferring with <code>postMessage()</code></a></li>
</ul>
</li>
<li><a href="#class-readablestreamdefaultreader">Class: <code>ReadableStreamDefaultReader</code></a><ul>
<li><a href="#new-readablestreamdefaultreaderstream"><code>new ReadableStreamDefaultReader(stream)</code></a></li>
<li><a href="#readablestreamdefaultreadercancelreason"><code>readableStreamDefaultReader.cancel([reason])</code></a></li>
<li><a href="#readablestreamdefaultreaderclosed"><code>readableStreamDefaultReader.closed</code></a></li>
<li><a href="#readablestreamdefaultreaderread"><code>readableStreamDefaultReader.read()</code></a></li>
<li><a href="#readablestreamdefaultreaderreleaselock"><code>readableStreamDefaultReader.releaseLock()</code></a></li>
</ul>
</li>
<li><a href="#class-readablestreambyobreader">Class: <code>ReadableStreamBYOBReader</code></a><ul>
<li><a href="#new-readablestreambyobreaderstream"><code>new ReadableStreamBYOBReader(stream)</code></a></li>
<li><a href="#readablestreambyobreadercancelreason"><code>readableStreamBYOBReader.cancel([reason])</code></a></li>
<li><a href="#readablestreambyobreaderclosed"><code>readableStreamBYOBReader.closed</code></a></li>
<li><a href="#readablestreambyobreaderreadview"><code>readableStreamBYOBReader.read(view)</code></a></li>
<li><a href="#readablestreambyobreaderreleaselock"><code>readableStreamBYOBReader.releaseLock()</code></a></li>
</ul>
</li>
<li><a href="#class-readablestreamdefaultcontroller">Class: <code>ReadableStreamDefaultController</code></a><ul>
<li><a href="#readablestreamdefaultcontrollerclose"><code>readableStreamDefaultController.close()</code></a></li>
<li><a href="#readablestreamdefaultcontrollerdesiredsize"><code>readableStreamDefaultController.desiredSize</code></a></li>
<li><a href="#readablestreamdefaultcontrollerenqueuechunk"><code>readableStreamDefaultController.enqueue([chunk])</code></a></li>
<li><a href="#readablestreamdefaultcontrollererrorerror"><code>readableStreamDefaultController.error([error])</code></a></li>
</ul>
</li>
<li><a href="#class-readablebytestreamcontroller">Class: <code>ReadableByteStreamController</code></a><ul>
<li><a href="#readablebytestreamcontrollerbyobrequest"><code>readableByteStreamController.byobRequest</code></a></li>
<li><a href="#readablebytestreamcontrollerclose"><code>readableByteStreamController.close()</code></a></li>
<li><a href="#readablebytestreamcontrollerdesiredsize"><code>readableByteStreamController.desiredSize</code></a></li>
<li><a href="#readablebytestreamcontrollerenqueuechunk"><code>readableByteStreamController.enqueue(chunk)</code></a></li>
<li><a href="#readablebytestreamcontrollererrorerror"><code>readableByteStreamController.error([error])</code></a></li>
</ul>
</li>
<li><a href="#class-readablestreambyobrequest">Class: <code>ReadableStreamBYOBRequest</code></a><ul>
<li><a href="#readablestreambyobrequestrespondbyteswritten"><code>readableStreamBYOBRequest.respond(bytesWritten)</code></a></li>
<li><a href="#readablestreambyobrequestrespondwithnewviewview"><code>readableStreamBYOBRequest.respondWithNewView(view)</code></a></li>
<li><a href="#readablestreambyobrequestview"><code>readableStreamBYOBRequest.view</code></a></li>
</ul>
</li>
<li><a href="#class-writablestream">Class: <code>WritableStream</code></a><ul>
<li><a href="#new-writablestreamunderlyingsink-strategy"><code>new WritableStream([underlyingSink[, strategy]])</code></a></li>
<li><a href="#writablestreamabortreason"><code>writableStream.abort([reason])</code></a></li>
<li><a href="#writablestreamclose"><code>writableStream.close()</code></a></li>
<li><a href="#writablestreamgetwriter"><code>writableStream.getWriter()</code></a></li>
<li><a href="#writablestreamlocked"><code>writableStream.locked</code></a></li>
<li><a href="#transferring-with-postmessage_1">Transferring with postMessage()</a></li>
</ul>
</li>
<li><a href="#class-writablestreamdefaultwriter">Class: <code>WritableStreamDefaultWriter</code></a><ul>
<li><a href="#new-writablestreamdefaultwriterstream"><code>new WritableStreamDefaultWriter(stream)</code></a></li>
<li><a href="#writablestreamdefaultwriterabortreason"><code>writableStreamDefaultWriter.abort([reason])</code></a></li>
<li><a href="#writablestreamdefaultwriterclose"><code>writableStreamDefaultWriter.close()</code></a></li>
<li><a href="#writablestreamdefaultwriterclosed"><code>writableStreamDefaultWriter.closed</code></a></li>
<li><a href="#writablestreamdefaultwriterdesiredsize"><code>writableStreamDefaultWriter.desiredSize</code></a></li>
<li><a href="#writablestreamdefaultwriterready"><code>writableStreamDefaultWriter.ready</code></a></li>
<li><a href="#writablestreamdefaultwriterreleaselock"><code>writableStreamDefaultWriter.releaseLock()</code></a></li>
<li><a href="#writablestreamdefaultwriterwritechunk"><code>writableStreamDefaultWriter.write([chunk])</code></a></li>
</ul>
</li>
<li><a href="#class-writablestreamdefaultcontroller">Class: <code>WritableStreamDefaultController</code></a><ul>
<li><a href="#writablestreamdefaultcontrollererrorerror"><code>writableStreamDefaultController.error([error])</code></a></li>
<li><a href="#writablestreamdefaultcontrollersignal"><code>writableStreamDefaultController.signal</code></a></li>
</ul>
</li>
<li><a href="#class-transformstream">Class: <code>TransformStream</code></a><ul>
<li><a href="#new-transformstreamtransformer-writablestrategy-readablestrategy"><code>new TransformStream([transformer[, writableStrategy[, readableStrategy]]])</code></a></li>
<li><a href="#transformstreamreadable"><code>transformStream.readable</code></a></li>
<li><a href="#transformstreamwritable"><code>transformStream.writable</code></a></li>
<li><a href="#transferring-with-postmessage_2">Transferring with postMessage()</a></li>
</ul>
</li>
<li><a href="#class-transformstreamdefaultcontroller">Class: <code>TransformStreamDefaultController</code></a><ul>
<li><a href="#transformstreamdefaultcontrollerdesiredsize"><code>transformStreamDefaultController.desiredSize</code></a></li>
<li><a href="#transformstreamdefaultcontrollerenqueuechunk"><code>transformStreamDefaultController.enqueue([chunk])</code></a></li>
<li><a href="#transformstreamdefaultcontrollererrorreason"><code>transformStreamDefaultController.error([reason])</code></a></li>
<li><a href="#transformstreamdefaultcontrollerterminate"><code>transformStreamDefaultController.terminate()</code></a></li>
</ul>
</li>
<li><a href="#class-bytelengthqueuingstrategy">Class: <code>ByteLengthQueuingStrategy</code></a><ul>
<li><a href="#new-bytelengthqueuingstrategyinit"><code>new ByteLengthQueuingStrategy(init)</code></a></li>
<li><a href="#bytelengthqueuingstrategyhighwatermark"><code>byteLengthQueuingStrategy.highWaterMark</code></a></li>
<li><a href="#bytelengthqueuingstrategysize"><code>byteLengthQueuingStrategy.size</code></a></li>
</ul>
</li>
<li><a href="#class-countqueuingstrategy">Class: <code>CountQueuingStrategy</code></a><ul>
<li><a href="#new-countqueuingstrategyinit"><code>new CountQueuingStrategy(init)</code></a></li>
<li><a href="#countqueuingstrategyhighwatermark"><code>countQueuingStrategy.highWaterMark</code></a></li>
<li><a href="#countqueuingstrategysize"><code>countQueuingStrategy.size</code></a></li>
</ul>
</li>
<li><a href="#class-textencoderstream">Class: <code>TextEncoderStream</code></a><ul>
<li><a href="#new-textencoderstream"><code>new TextEncoderStream()</code></a></li>
<li><a href="#textencoderstreamencoding"><code>textEncoderStream.encoding</code></a></li>
<li><a href="#textencoderstreamreadable"><code>textEncoderStream.readable</code></a></li>
<li><a href="#textencoderstreamwritable"><code>textEncoderStream.writable</code></a></li>
</ul>
</li>
<li><a href="#class-textdecoderstream">Class: <code>TextDecoderStream</code></a><ul>
<li><a href="#new-textdecoderstreamencoding-options"><code>new TextDecoderStream([encoding[, options]])</code></a></li>
<li><a href="#textdecoderstreamencoding"><code>textDecoderStream.encoding</code></a></li>
<li><a href="#textdecoderstreamfatal"><code>textDecoderStream.fatal</code></a></li>
<li><a href="#textdecoderstreamignorebom"><code>textDecoderStream.ignoreBOM</code></a></li>
<li><a href="#textdecoderstreamreadable"><code>textDecoderStream.readable</code></a></li>
<li><a href="#textdecoderstreamwritable"><code>textDecoderStream.writable</code></a></li>
</ul>
</li>
<li><a href="#class-compressionstream">Class: <code>CompressionStream</code></a><ul>
<li><a href="#new-compressionstreamformat"><code>new CompressionStream(format)</code></a></li>
<li><a href="#compressionstreamreadable"><code>compressionStream.readable</code></a></li>
<li><a href="#compressionstreamwritable"><code>compressionStream.writable</code></a></li>
</ul>
</li>
<li><a href="#class-decompressionstream">Class: <code>DecompressionStream</code></a><ul>
<li><a href="#new-decompressionstreamformat"><code>new DecompressionStream(format)</code></a></li>
<li><a href="#decompressionstreamreadable"><code>decompressionStream.readable</code></a></li>
<li><a href="#decompressionstreamwritable"><code>decompressionStream.writable</code></a></li>
</ul>
</li>
<li><a href="#utility-consumers">Utility Consumers</a><ul>
<li><a href="#streamconsumersarraybufferstream"><code>streamConsumers.arrayBuffer(stream)</code></a></li>
<li><a href="#streamconsumersblobstream"><code>streamConsumers.blob(stream)</code></a></li>
<li><a href="#streamconsumersbufferstream"><code>streamConsumers.buffer(stream)</code></a></li>
<li><a href="#streamconsumersjsonstream"><code>streamConsumers.json(stream)</code></a></li>
<li><a href="#streamconsumerstextstream"><code>streamConsumers.text(stream)</code></a></li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
</ul>
</details>
<div id="apicontent">
<h2>Web Streams API<span><a class="mark" href="#web-streams-api" id="web-streams-api">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_web_streams_api"></a></h2>
<!--introduced_in=v16.5.0-->
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>Use of this API no longer emit a runtime warning.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><blockquote>
<p>Stability: 1 - Experimental.</p>
</blockquote>
<p>An implementation of the <a href="https://streams.spec.whatwg.org/">WHATWG Streams Standard</a>.</p>
<section><h3>Overview<span><a class="mark" href="#overview" id="overview">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_overview"></a></h3>
<p>The <a href="https://streams.spec.whatwg.org/">WHATWG Streams Standard</a> (or "web streams") defines an API for handling
streaming data. It is similar to the Node.js <a href="stream.html">Streams</a> API but emerged later
and has become the "standard" API for streaming data across many JavaScript
environments.</p>
<p>There are three primary types of objects:</p>
<ul>
<li><code>ReadableStream</code> - Represents a source of streaming data.</li>
<li><code>WritableStream</code> - Represents a destination for streaming data.</li>
<li><code>TransformStream</code> - Represents an algorithm for transforming streaming data.</li>
</ul>
<h4>Example <code>ReadableStream</code><span><a class="mark" href="#example-readablestream" id="example-readablestream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_example_readablestream"></a></h4>
<p>This example creates a simple <code>ReadableStream</code> that pushes the current
<code>performance.now()</code> timestamp once every second forever. An async iterable
is used to read the data from the stream.</p>
<pre><code class="language-mjs">import {
ReadableStream,
} from 'node:stream/web';
import {
setInterval as every,
} from 'node:timers/promises';
import {
performance,
} from 'node:perf_hooks';
const SECOND = 1000;
const stream = new ReadableStream({
async start(controller) {
for await (const _ of every(SECOND))
controller.enqueue(performance.now());
},
});
for await (const value of stream)
console.log(value);
</code></pre>
<pre><code class="language-cjs">const {
ReadableStream,
} = require('node:stream/web');
const {
setInterval: every,
} = require('node:timers/promises');
const {
performance,
} = require('node:perf_hooks');
const SECOND = 1000;
const stream = new ReadableStream({
async start(controller) {
for await (const _ of every(SECOND))
controller.enqueue(performance.now());
},
});
(async () => {
for await (const value of stream)
console.log(value);
})();
</code></pre>
</section><section><h3>API<span><a class="mark" href="#api" id="api">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_api"></a></h3>
<h4>Class: <code>ReadableStream</code><span><a class="mark" href="#class-readablestream" id="class-readablestream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_readablestream"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><h5><code>new ReadableStream([underlyingSource [, strategy]])</code><span><a class="mark" href="#new-readablestreamunderlyingsource--strategy" id="new-readablestreamunderlyingsource--strategy">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_readablestream_underlyingsource_strategy"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><!--lint disable maximum-line-length remark-lint-->
<ul>
<li><code>underlyingSource</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is invoked immediately when
the <code>ReadableStream</code> is created.<ul>
<li><code>controller</code> {ReadableStreamDefaultController|ReadableByteStreamController}</li>
<li>Returns: <code>undefined</code> or a promise fulfilled with <code>undefined</code>.</li>
</ul>
</li>
<li><code>pull</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called repeatedly when the
<code>ReadableStream</code> internal queue is not full. The operation may be sync or
async. If async, the function will not be called again until the previously
returned promise is fulfilled.<ul>
<li><code>controller</code> {ReadableStreamDefaultController|ReadableByteStreamController}</li>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
</li>
<li><code>cancel</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called when the
<code>ReadableStream</code> is canceled.<ul>
<li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
</li>
<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Must be <code>'bytes'</code> or <code>undefined</code>.</li>
<li><code>autoAllocateChunkSize</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Used only when <code>type</code> is equal to
<code>'bytes'</code>. When set to a non-zero value a view buffer is automatically
allocated to <code>ReadableByteStreamController.byobRequest</code>. When not set
one must use stream's internal queues to transfer data via the default
reader <code>ReadableStreamDefaultReader</code>.</li>
</ul>
</li>
<li><code>strategy</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The maximum internal queue size before backpressure
is applied.</li>
<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function used to identify the size of each
chunk of data.<ul>
<li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
</li>
</ul>
</li>
</ul>
<!--lint enable maximum-line-length remark-lint-->
<h5><code>readableStream.locked</code><span><a class="mark" href="#readablestreamlocked" id="readablestreamlocked">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_locked"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Set to <code>true</code> if there is an active reader for this
<a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.</li>
</ul>
<p>The <code>readableStream.locked</code> property is <code>false</code> by default, and is
switched to <code>true</code> while there is an active reader consuming the
stream's data.</p>
<h5><code>readableStream.cancel([reason])</code><span><a class="mark" href="#readablestreamcancelreason" id="readablestreamcancelreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_cancel_reason"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: A promise fulfilled with <code>undefined</code> once cancelation has
been completed.</li>
</ul>
<h5><code>readableStream.getReader([options])</code><span><a class="mark" href="#readablestreamgetreaderoptions" id="readablestreamgetreaderoptions">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_getreader_options"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>mode</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <code>'byob'</code> or <code>undefined</code></li>
</ul>
</li>
<li>Returns: {ReadableStreamDefaultReader|ReadableStreamBYOBReader}</li>
</ul>
<pre><code class="language-mjs">import { ReadableStream } from 'node:stream/web';
const stream = new ReadableStream();
const reader = stream.getReader();
console.log(await reader.read());
</code></pre>
<pre><code class="language-cjs">const { ReadableStream } = require('node:stream/web');
const stream = new ReadableStream();
const reader = stream.getReader();
reader.read().then(console.log);
</code></pre>
<p>Causes the <code>readableStream.locked</code> to be <code>true</code>.</p>
<h5><code>readableStream.pipeThrough(transform[, options])</code><span><a class="mark" href="#readablestreampipethroughtransform-options" id="readablestreampipethroughtransform-options">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_pipethrough_transform_options"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>transform</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>readable</code> <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> The <code>ReadableStream</code> to which
<code>transform.writable</code> will push the potentially modified data
is receives from this <code>ReadableStream</code>.</li>
<li><code>writable</code> <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> The <code>WritableStream</code> to which this
<code>ReadableStream</code>'s data will be written.</li>
</ul>
</li>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>preventAbort</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, errors in this <code>ReadableStream</code>
will not cause <code>transform.writable</code> to be aborted.</li>
<li><code>preventCancel</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, errors in the destination
<code>transform.writable</code> do not cause this <code>ReadableStream</code> to be
canceled.</li>
<li><code>preventClose</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, closing this <code>ReadableStream</code>
does not cause <code>transform.writable</code> to be closed.</li>
<li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows the transfer of data to be canceled
using an <a href="globals.html#class-abortcontroller" class="type"><AbortController></a>.</li>
</ul>
</li>
<li>Returns: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> From <code>transform.readable</code>.</li>
</ul>
<p>Connects this <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to the pair of <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and
<a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> provided in the <code>transform</code> argument such that the
data from this <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> is written in to <code>transform.writable</code>,
possibly transformed, then pushed to <code>transform.readable</code>. Once the
pipeline is configured, <code>transform.readable</code> is returned.</p>
<p>Causes the <code>readableStream.locked</code> to be <code>true</code> while the pipe operation
is active.</p>
<pre><code class="language-mjs">import {
ReadableStream,
TransformStream,
} from 'node:stream/web';
const stream = new ReadableStream({
start(controller) {
controller.enqueue('a');
},
});
const transform = new TransformStream({
transform(chunk, controller) {
controller.enqueue(chunk.toUpperCase());
},
});
const transformedStream = stream.pipeThrough(transform);
for await (const chunk of transformedStream)
console.log(chunk);
</code></pre>
<pre><code class="language-cjs">const {
ReadableStream,
TransformStream,
} = require('node:stream/web');
const stream = new ReadableStream({
start(controller) {
controller.enqueue('a');
},
});
const transform = new TransformStream({
transform(chunk, controller) {
controller.enqueue(chunk.toUpperCase());
},
});
const transformedStream = stream.pipeThrough(transform);
(async () => {
for await (const chunk of transformedStream)
console.log(chunk);
})();
</code></pre>
<h5><code>readableStream.pipeTo(destination[, options])</code><span><a class="mark" href="#readablestreampipetodestination-options" id="readablestreampipetodestination-options">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_pipeto_destination_options"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>destination</code> <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> A <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> to which this
<code>ReadableStream</code>'s data will be written.</li>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>preventAbort</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, errors in this <code>ReadableStream</code>
will not cause <code>destination</code> to be aborted.</li>
<li><code>preventCancel</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, errors in the <code>destination</code>
will not cause this <code>ReadableStream</code> to be canceled.</li>
<li><code>preventClose</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, closing this <code>ReadableStream</code>
does not cause <code>destination</code> to be closed.</li>
<li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows the transfer of data to be canceled
using an <a href="globals.html#class-abortcontroller" class="type"><AbortController></a>.</li>
</ul>
</li>
<li>Returns: A promise fulfilled with <code>undefined</code></li>
</ul>
<p>Causes the <code>readableStream.locked</code> to be <code>true</code> while the pipe operation
is active.</p>
<h5><code>readableStream.tee()</code><span><a class="mark" href="#readablestreamtee" id="readablestreamtee">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_tee"></a></h5>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.10.0</td>
<td><p>Support teeing a readable byte stream.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><ul>
<li>Returns: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream[]></a></li>
</ul>
<p>Returns a pair of new <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> instances to which this
<code>ReadableStream</code>'s data will be forwarded. Each will receive the
same data.</p>
<p>Causes the <code>readableStream.locked</code> to be <code>true</code>.</p>
<h5><code>readableStream.values([options])</code><span><a class="mark" href="#readablestreamvaluesoptions" id="readablestreamvaluesoptions">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_values_options"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>preventCancel</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, prevents the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>
from being closed when the async iterator abruptly terminates.
<strong>Default</strong>: <code>false</code>.</li>
</ul>
</li>
</ul>
<p>Creates and returns an async iterator usable for consuming this
<code>ReadableStream</code>'s data.</p>
<p>Causes the <code>readableStream.locked</code> to be <code>true</code> while the async iterator
is active.</p>
<pre><code class="language-mjs">import { Buffer } from 'node:buffer';
const stream = new ReadableStream(getSomeSource());
for await (const chunk of stream.values({ preventCancel: true }))
console.log(Buffer.from(chunk).toString());
</code></pre>
<h5>Async Iteration<span><a class="mark" href="#async-iteration" id="async-iteration">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_async_iteration"></a></h5>
<p>The <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> object supports the async iterator protocol using
<code>for await</code> syntax.</p>
<pre><code class="language-mjs">import { Buffer } from 'node:buffer';
const stream = new ReadableStream(getSomeSource());
for await (const chunk of stream)
console.log(Buffer.from(chunk).toString());
</code></pre>
<p>The async iterator will consume the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> until it terminates.</p>
<p>By default, if the async iterator exits early (via either a <code>break</code>,
<code>return</code>, or a <code>throw</code>), the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> will be closed. To prevent
automatic closing of the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>, use the <code>readableStream.values()</code>
method to acquire the async iterator and set the <code>preventCancel</code> option to
<code>true</code>.</p>
<p>The <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> must not be locked (that is, it must not have an existing
active reader). During the async iteration, the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> will be locked.</p>
<h5>Transferring with <code>postMessage()</code><span><a class="mark" href="#transferring-with-postmessage" id="transferring-with-postmessage">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transferring_with_postmessage"></a></h5>
<p>A <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> instance can be transferred using a <a href="worker_threads.html#class-messageport" class="type"><MessagePort></a>.</p>
<pre><code class="language-js">const stream = new ReadableStream(getReadableSourceSomehow());
const { port1, port2 } = new MessageChannel();
port1.onmessage = ({ data }) => {
data.getReader().read().then((chunk) => {
console.log(chunk);
});
};
port2.postMessage(stream, [stream]);
</code></pre>
<h4>Class: <code>ReadableStreamDefaultReader</code><span><a class="mark" href="#class-readablestreamdefaultreader" id="class-readablestreamdefaultreader">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_readablestreamdefaultreader"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><p>By default, calling <code>readableStream.getReader()</code> with no arguments
will return an instance of <code>ReadableStreamDefaultReader</code>. The default
reader treats the chunks of data passed through the stream as opaque
values, which allows the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to work with generally any
JavaScript value.</p>
<h5><code>new ReadableStreamDefaultReader(stream)</code><span><a class="mark" href="#new-readablestreamdefaultreaderstream" id="new-readablestreamdefaultreaderstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_readablestreamdefaultreader_stream"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>stream</code> <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li>
</ul>
<p>Creates a new <a href="webstreams.html#class-readablestreamdefaultreader" class="type"><ReadableStreamDefaultReader></a> that is locked to the
given <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.</p>
<h5><code>readableStreamDefaultReader.cancel([reason])</code><span><a class="mark" href="#readablestreamdefaultreadercancelreason" id="readablestreamdefaultreadercancelreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultreader_cancel_reason"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
<p>Cancels the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and returns a promise that is fulfilled
when the underlying stream has been canceled.</p>
<h5><code>readableStreamDefaultReader.closed</code><span><a class="mark" href="#readablestreamdefaultreaderclosed" id="readablestreamdefaultreaderclosed">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultreader_closed"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfilled with <code>undefined</code> when the associated
<a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> is closed or rejected if the stream errors or the reader's
lock is released before the stream finishes closing.</li>
</ul>
<h5><code>readableStreamDefaultReader.read()</code><span><a class="mark" href="#readablestreamdefaultreaderread" id="readablestreamdefaultreaderread">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultreader_read"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Returns: A promise fulfilled with an object:<ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a></li>
<li><code>done</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
</li>
</ul>
<p>Requests the next chunk of data from the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>
and returns a promise that is fulfilled with the data once it is
available.</p>
<h5><code>readableStreamDefaultReader.releaseLock()</code><span><a class="mark" href="#readablestreamdefaultreaderreleaselock" id="readablestreamdefaultreaderreleaselock">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultreader_releaselock"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><p>Releases this reader's lock on the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.</p>
<h4>Class: <code>ReadableStreamBYOBReader</code><span><a class="mark" href="#class-readablestreambyobreader" id="class-readablestreambyobreader">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_readablestreambyobreader"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><p>The <code>ReadableStreamBYOBReader</code> is an alternative consumer for
byte-oriented <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>s (those that are created with
<code>underlyingSource.type</code> set equal to <code>'bytes'</code> when the
<code>ReadableStream</code> was created).</p>
<p>The <code>BYOB</code> is short for "bring your own buffer". This is a
pattern that allows for more efficient reading of byte-oriented
data that avoids extraneous copying.</p>
<pre><code class="language-mjs">import {
open,
} from 'node:fs/promises';
import {
ReadableStream,
} from 'node:stream/web';
import { Buffer } from 'node:buffer';
class Source {
type = 'bytes';
autoAllocateChunkSize = 1024;
async start(controller) {
this.file = await open(new URL(import.meta.url));
this.controller = controller;
}
async pull(controller) {
const view = controller.byobRequest?.view;
const {
bytesRead,
} = await this.file.read({
buffer: view,
offset: view.byteOffset,
length: view.byteLength,
});
if (bytesRead === 0) {
await this.file.close();
this.controller.close();
}
controller.byobRequest.respond(bytesRead);
}
}
const stream = new ReadableStream(new Source());
async function read(stream) {
const reader = stream.getReader({ mode: 'byob' });
const chunks = [];
let result;
do {
result = await reader.read(Buffer.alloc(100));
if (result.value !== undefined)
chunks.push(Buffer.from(result.value));
} while (!result.done);
return Buffer.concat(chunks);
}
const data = await read(stream);
console.log(Buffer.from(data).toString());
</code></pre>
<h5><code>new ReadableStreamBYOBReader(stream)</code><span><a class="mark" href="#new-readablestreambyobreaderstream" id="new-readablestreambyobreaderstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_readablestreambyobreader_stream"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>stream</code> <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li>
</ul>
<p>Creates a new <code>ReadableStreamBYOBReader</code> that is locked to the
given <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.</p>
<h5><code>readableStreamBYOBReader.cancel([reason])</code><span><a class="mark" href="#readablestreambyobreadercancelreason" id="readablestreambyobreadercancelreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobreader_cancel_reason"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
<p>Cancels the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and returns a promise that is fulfilled
when the underlying stream has been canceled.</p>
<h5><code>readableStreamBYOBReader.closed</code><span><a class="mark" href="#readablestreambyobreaderclosed" id="readablestreambyobreaderclosed">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobreader_closed"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfilled with <code>undefined</code> when the associated
<a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> is closed or rejected if the stream errors or the reader's
lock is released before the stream finishes closing.</li>
</ul>
<h5><code>readableStreamBYOBReader.read(view)</code><span><a class="mark" href="#readablestreambyobreaderreadview" id="readablestreambyobreaderreadview">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobreader_read_view"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>view</code> {Buffer|TypedArray|DataView}</li>
<li>Returns: A promise fulfilled with an object:<ul>
<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a></li>
<li><code>done</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
</li>
</ul>
<p>Requests the next chunk of data from the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>
and returns a promise that is fulfilled with the data once it is
available.</p>
<p>Do not pass a pooled <a href="buffer.html#class-buffer" class="type"><Buffer></a> object instance in to this method.
Pooled <code>Buffer</code> objects are created using <code>Buffer.allocUnsafe()</code>,
or <code>Buffer.from()</code>, or are often returned by various <code>node:fs</code> module
callbacks. These types of <code>Buffer</code>s use a shared underlying
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a> object that contains all of the data from all of
the pooled <code>Buffer</code> instances. When a <code>Buffer</code>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a>,
or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> is passed in to <code>readableStreamBYOBReader.read()</code>,
the view's underlying <code>ArrayBuffer</code> is <em>detached</em>, invalidating
all existing views that may exist on that <code>ArrayBuffer</code>. This
can have disastrous consequences for your application.</p>
<h5><code>readableStreamBYOBReader.releaseLock()</code><span><a class="mark" href="#readablestreambyobreaderreleaselock" id="readablestreambyobreaderreleaselock">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobreader_releaselock"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><p>Releases this reader's lock on the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.</p>
<h4>Class: <code>ReadableStreamDefaultController</code><span><a class="mark" href="#class-readablestreamdefaultcontroller" id="class-readablestreamdefaultcontroller">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_readablestreamdefaultcontroller"></a></h4>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><p>Every <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> has a controller that is responsible for
the internal state and management of the stream's queue. The
<code>ReadableStreamDefaultController</code> is the default controller
implementation for <code>ReadableStream</code>s that are not byte-oriented.</p>
<h5><code>readableStreamDefaultController.close()</code><span><a class="mark" href="#readablestreamdefaultcontrollerclose" id="readablestreamdefaultcontrollerclose">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultcontroller_close"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><p>Closes the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to which this controller is associated.</p>
<h5><code>readableStreamDefaultController.desiredSize</code><span><a class="mark" href="#readablestreamdefaultcontrollerdesiredsize" id="readablestreamdefaultcontrollerdesiredsize">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultcontroller_desiredsize"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
<p>Returns the amount of data remaining to fill the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>'s
queue.</p>
<h5><code>readableStreamDefaultController.enqueue([chunk])</code><span><a class="mark" href="#readablestreamdefaultcontrollerenqueuechunk" id="readablestreamdefaultcontrollerenqueuechunk">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultcontroller_enqueue_chunk"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
</ul>
<p>Appends a new chunk of data to the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>'s queue.</p>
<h5><code>readableStreamDefaultController.error([error])</code><span><a class="mark" href="#readablestreamdefaultcontrollererrorerror" id="readablestreamdefaultcontrollererrorerror">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultcontroller_error_error"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
</ul>
<p>Signals an error that causes the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to error and close.</p>
<h4>Class: <code>ReadableByteStreamController</code><span><a class="mark" href="#class-readablebytestreamcontroller" id="class-readablebytestreamcontroller">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_readablebytestreamcontroller"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.10.0</td>
<td><p>Support handling a BYOB pull request from a released reader.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><p>Every <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> has a controller that is responsible for
the internal state and management of the stream's queue. The
<code>ReadableByteStreamController</code> is for byte-oriented <code>ReadableStream</code>s.</p>
<h5><code>readableByteStreamController.byobRequest</code><span><a class="mark" href="#readablebytestreamcontrollerbyobrequest" id="readablebytestreamcontrollerbyobrequest">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablebytestreamcontroller_byobrequest"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="webstreams.html#class-readablestreambyobrequest" class="type"><ReadableStreamBYOBRequest></a></li>
</ul>
<h5><code>readableByteStreamController.close()</code><span><a class="mark" href="#readablebytestreamcontrollerclose" id="readablebytestreamcontrollerclose">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablebytestreamcontroller_close"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><p>Closes the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to which this controller is associated.</p>
<h5><code>readableByteStreamController.desiredSize</code><span><a class="mark" href="#readablebytestreamcontrollerdesiredsize" id="readablebytestreamcontrollerdesiredsize">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablebytestreamcontroller_desiredsize"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
<p>Returns the amount of data remaining to fill the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>'s
queue.</p>
<h5><code>readableByteStreamController.enqueue(chunk)</code><span><a class="mark" href="#readablebytestreamcontrollerenqueuechunk" id="readablebytestreamcontrollerenqueuechunk">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablebytestreamcontroller_enqueue_chunk"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>chunk</code>: {Buffer|TypedArray|DataView}</li>
</ul>
<p>Appends a new chunk of data to the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>'s queue.</p>
<h5><code>readableByteStreamController.error([error])</code><span><a class="mark" href="#readablebytestreamcontrollererrorerror" id="readablebytestreamcontrollererrorerror">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablebytestreamcontroller_error_error"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
</ul>
<p>Signals an error that causes the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to error and close.</p>
<h4>Class: <code>ReadableStreamBYOBRequest</code><span><a class="mark" href="#class-readablestreambyobrequest" id="class-readablestreambyobrequest">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_readablestreambyobrequest"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><p>When using <code>ReadableByteStreamController</code> in byte-oriented
streams, and when using the <code>ReadableStreamBYOBReader</code>,
the <code>readableByteStreamController.byobRequest</code> property
provides access to a <code>ReadableStreamBYOBRequest</code> instance
that represents the current read request. The object
is used to gain access to the <code>ArrayBuffer</code>/<code>TypedArray</code>
that has been provided for the read request to fill,
and provides methods for signaling that the data has
been provided.</p>
<h5><code>readableStreamBYOBRequest.respond(bytesWritten)</code><span><a class="mark" href="#readablestreambyobrequestrespondbyteswritten" id="readablestreambyobrequestrespondbyteswritten">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobrequest_respond_byteswritten"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>bytesWritten</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
<p>Signals that a <code>bytesWritten</code> number of bytes have been written
to <code>readableStreamBYOBRequest.view</code>.</p>
<h5><code>readableStreamBYOBRequest.respondWithNewView(view)</code><span><a class="mark" href="#readablestreambyobrequestrespondwithnewviewview" id="readablestreambyobrequestrespondwithnewviewview">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobrequest_respondwithnewview_view"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>view</code> {Buffer|TypedArray|DataView}</li>
</ul>
<p>Signals that the request has been fulfilled with bytes written
to a new <code>Buffer</code>, <code>TypedArray</code>, or <code>DataView</code>.</p>
<h5><code>readableStreamBYOBRequest.view</code><span><a class="mark" href="#readablestreambyobrequestview" id="readablestreambyobrequestview">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobrequest_view"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: {Buffer|TypedArray|DataView}</li>
</ul>
<h4>Class: <code>WritableStream</code><span><a class="mark" href="#class-writablestream" id="class-writablestream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_writablestream"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><p>The <code>WritableStream</code> is a destination to which stream data is sent.</p>
<pre><code class="language-mjs">import {
WritableStream,
} from 'node:stream/web';
const stream = new WritableStream({
write(chunk) {
console.log(chunk);
},
});
await stream.getWriter().write('Hello World');
</code></pre>
<h5><code>new WritableStream([underlyingSink[, strategy]])</code><span><a class="mark" href="#new-writablestreamunderlyingsink-strategy" id="new-writablestreamunderlyingsink-strategy">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_writablestream_underlyingsink_strategy"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>underlyingSink</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is invoked immediately when
the <code>WritableStream</code> is created.<ul>
<li><code>controller</code> <a href="webstreams.html#class-writablestreamdefaultcontroller" class="type"><WritableStreamDefaultController></a></li>
<li>Returns: <code>undefined</code> or a promise fulfilled with <code>undefined</code>.</li>
</ul>
</li>
<li><code>write</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is invoked when a chunk of
data has been written to the <code>WritableStream</code>.<ul>
<li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li><code>controller</code> <a href="webstreams.html#class-writablestreamdefaultcontroller" class="type"><WritableStreamDefaultController></a></li>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
</li>
<li><code>close</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called when the
<code>WritableStream</code> is closed.<ul>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
</li>
<li><code>abort</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called to abruptly close
the <code>WritableStream</code>.<ul>
<li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
</li>
<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The <code>type</code> option is reserved for future use and <em>must</em> be
undefined.</li>
</ul>
</li>
<li><code>strategy</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The maximum internal queue size before backpressure
is applied.</li>
<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function used to identify the size of each
chunk of data.<ul>
<li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
</li>
</ul>
</li>
</ul>
<h5><code>writableStream.abort([reason])</code><span><a class="mark" href="#writablestreamabortreason" id="writablestreamabortreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestream_abort_reason"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
<p>Abruptly terminates the <code>WritableStream</code>. All queued writes will be
canceled with their associated promises rejected.</p>
<h5><code>writableStream.close()</code><span><a class="mark" href="#writablestreamclose" id="writablestreamclose">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestream_close"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
<p>Closes the <code>WritableStream</code> when no additional writes are expected.</p>
<h5><code>writableStream.getWriter()</code><span><a class="mark" href="#writablestreamgetwriter" id="writablestreamgetwriter">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestream_getwriter"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Returns: <a href="webstreams.html#class-writablestreamdefaultwriter" class="type"><WritableStreamDefaultWriter></a></li>
</ul>
<p>Creates and returns a new writer instance that can be used to write
data into the <code>WritableStream</code>.</p>
<h5><code>writableStream.locked</code><span><a class="mark" href="#writablestreamlocked" id="writablestreamlocked">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestream_locked"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
<p>The <code>writableStream.locked</code> property is <code>false</code> by default, and is
switched to <code>true</code> while there is an active writer attached to this
<code>WritableStream</code>.</p>
<h5>Transferring with postMessage()<span><a class="mark" href="#transferring-with-postmessage_1" id="transferring-with-postmessage_1">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transferring_with_postmessage_1"></a></h5>
<p>A <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> instance can be transferred using a <a href="worker_threads.html#class-messageport" class="type"><MessagePort></a>.</p>
<pre><code class="language-js">const stream = new WritableStream(getWritableSinkSomehow());
const { port1, port2 } = new MessageChannel();
port1.onmessage = ({ data }) => {
data.getWriter().write('hello');
};
port2.postMessage(stream, [stream]);
</code></pre>
<h4>Class: <code>WritableStreamDefaultWriter</code><span><a class="mark" href="#class-writablestreamdefaultwriter" id="class-writablestreamdefaultwriter">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_writablestreamdefaultwriter"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><h5><code>new WritableStreamDefaultWriter(stream)</code><span><a class="mark" href="#new-writablestreamdefaultwriterstream" id="new-writablestreamdefaultwriterstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_writablestreamdefaultwriter_stream"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>stream</code> <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a></li>
</ul>
<p>Creates a new <code>WritableStreamDefaultWriter</code> that is locked to the given
<code>WritableStream</code>.</p>
<h5><code>writableStreamDefaultWriter.abort([reason])</code><span><a class="mark" href="#writablestreamdefaultwriterabortreason" id="writablestreamdefaultwriterabortreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_abort_reason"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
<p>Abruptly terminates the <code>WritableStream</code>. All queued writes will be
canceled with their associated promises rejected.</p>
<h5><code>writableStreamDefaultWriter.close()</code><span><a class="mark" href="#writablestreamdefaultwriterclose" id="writablestreamdefaultwriterclose">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_close"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
<p>Closes the <code>WritableStream</code> when no additional writes are expected.</p>
<h5><code>writableStreamDefaultWriter.closed</code><span><a class="mark" href="#writablestreamdefaultwriterclosed" id="writablestreamdefaultwriterclosed">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_closed"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfilled with <code>undefined</code> when the associated
<a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> is closed or rejected if the stream errors or the writer's
lock is released before the stream finishes closing.</li>
</ul>
<h5><code>writableStreamDefaultWriter.desiredSize</code><span><a class="mark" href="#writablestreamdefaultwriterdesiredsize" id="writablestreamdefaultwriterdesiredsize">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_desiredsize"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
<p>The amount of data required to fill the <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>'s queue.</p>
<h5><code>writableStreamDefaultWriter.ready</code><span><a class="mark" href="#writablestreamdefaultwriterready" id="writablestreamdefaultwriterready">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_ready"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfilled with <code>undefined</code> when the writer is ready
to be used.</li>
</ul>
<h5><code>writableStreamDefaultWriter.releaseLock()</code><span><a class="mark" href="#writablestreamdefaultwriterreleaselock" id="writablestreamdefaultwriterreleaselock">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_releaselock"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><p>Releases this writer's lock on the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.</p>
<h5><code>writableStreamDefaultWriter.write([chunk])</code><span><a class="mark" href="#writablestreamdefaultwriterwritechunk" id="writablestreamdefaultwriterwritechunk">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_write_chunk"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>chunk</code>: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
<p>Appends a new chunk of data to the <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>'s queue.</p>
<h4>Class: <code>WritableStreamDefaultController</code><span><a class="mark" href="#class-writablestreamdefaultcontroller" id="class-writablestreamdefaultcontroller">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_writablestreamdefaultcontroller"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><p>The <code>WritableStreamDefaultController</code> manage's the <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>'s
internal state.</p>
<h5><code>writableStreamDefaultController.error([error])</code><span><a class="mark" href="#writablestreamdefaultcontrollererrorerror" id="writablestreamdefaultcontrollererrorerror">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultcontroller_error_error"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
</ul>
<p>Called by user-code to signal that an error has occurred while processing
the <code>WritableStream</code> data. When called, the <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> will be aborted,
with currently pending writes canceled.</p>
<h5><code>writableStreamDefaultController.signal</code><span><a class="mark" href="#writablestreamdefaultcontrollersignal" id="writablestreamdefaultcontrollersignal">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultcontroller_signal"></a></h5>
<ul>
<li>Type: <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> An <code>AbortSignal</code> that can be used to cancel pending
write or close operations when a <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> is aborted.</li>
</ul>
<h4>Class: <code>TransformStream</code><span><a class="mark" href="#class-transformstream" id="class-transformstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_transformstream"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><p>A <code>TransformStream</code> consists of a <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and a <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> that
are connected such that the data written to the <code>WritableStream</code> is received,
and potentially transformed, before being pushed into the <code>ReadableStream</code>'s
queue.</p>
<pre><code class="language-mjs">import {
TransformStream,
} from 'node:stream/web';
const transform = new TransformStream({
transform(chunk, controller) {
controller.enqueue(chunk.toUpperCase());
},
});
await Promise.all([
transform.writable.getWriter().write('A'),
transform.readable.getReader().read(),
]);
</code></pre>
<h5><code>new TransformStream([transformer[, writableStrategy[, readableStrategy]]])</code><span><a class="mark" href="#new-transformstreamtransformer-writablestrategy-readablestrategy" id="new-transformstreamtransformer-writablestrategy-readablestrategy">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_transformstream_transformer_writablestrategy_readablestrategy"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>transformer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is invoked immediately when
the <code>TransformStream</code> is created.<ul>
<li><code>controller</code> <a href="webstreams.html#class-transformstreamdefaultcontroller" class="type"><TransformStreamDefaultController></a></li>
<li>Returns: <code>undefined</code> or a promise fulfilled with <code>undefined</code></li>
</ul>
</li>
<li><code>transform</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that receives, and
potentially modifies, a chunk of data written to <code>transformStream.writable</code>,
before forwarding that on to <code>transformStream.readable</code>.<ul>
<li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li><code>controller</code> <a href="webstreams.html#class-transformstreamdefaultcontroller" class="type"><TransformStreamDefaultController></a></li>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
</li>
<li><code>flush</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called immediately before
the writable side of the <code>TransformStream</code> is closed, signaling the end of
the transformation process.<ul>
<li><code>controller</code> <a href="webstreams.html#class-transformstreamdefaultcontroller" class="type"><TransformStreamDefaultController></a></li>
<li>Returns: A promise fulfilled with <code>undefined</code>.</li>
</ul>
</li>
<li><code>readableType</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> the <code>readableType</code> option is reserved for future use
and <em>must</em> be <code>undefined</code>.</li>
<li><code>writableType</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> the <code>writableType</code> option is reserved for future use
and <em>must</em> be <code>undefined</code>.</li>
</ul>
</li>
<li><code>writableStrategy</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The maximum internal queue size before backpressure
is applied.</li>
<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function used to identify the size of each
chunk of data.<ul>
<li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
</li>
</ul>
</li>
<li><code>readableStrategy</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The maximum internal queue size before backpressure
is applied.</li>
<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function used to identify the size of each
chunk of data.<ul>
<li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
</li>
</ul>
</li>
</ul>
<h5><code>transformStream.readable</code><span><a class="mark" href="#transformstreamreadable" id="transformstreamreadable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transformstream_readable"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li>
</ul>
<h5><code>transformStream.writable</code><span><a class="mark" href="#transformstreamwritable" id="transformstreamwritable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transformstream_writable"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a></li>
</ul>
<h5>Transferring with postMessage()<span><a class="mark" href="#transferring-with-postmessage_2" id="transferring-with-postmessage_2">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transferring_with_postmessage_2"></a></h5>
<p>A <a href="webstreams.html#class-transformstream" class="type"><TransformStream></a> instance can be transferred using a <a href="worker_threads.html#class-messageport" class="type"><MessagePort></a>.</p>
<pre><code class="language-js">const stream = new TransformStream();
const { port1, port2 } = new MessageChannel();
port1.onmessage = ({ data }) => {
const { writable, readable } = data;
// ...
};
port2.postMessage(stream, [stream]);
</code></pre>
<h4>Class: <code>TransformStreamDefaultController</code><span><a class="mark" href="#class-transformstreamdefaultcontroller" id="class-transformstreamdefaultcontroller">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_transformstreamdefaultcontroller"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><p>The <code>TransformStreamDefaultController</code> manages the internal state
of the <code>TransformStream</code>.</p>
<h5><code>transformStreamDefaultController.desiredSize</code><span><a class="mark" href="#transformstreamdefaultcontrollerdesiredsize" id="transformstreamdefaultcontrollerdesiredsize">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transformstreamdefaultcontroller_desiredsize"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
<p>The amount of data required to fill the readable side's queue.</p>
<h5><code>transformStreamDefaultController.enqueue([chunk])</code><span><a class="mark" href="#transformstreamdefaultcontrollerenqueuechunk" id="transformstreamdefaultcontrollerenqueuechunk">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transformstreamdefaultcontroller_enqueue_chunk"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
</ul>
<p>Appends a chunk of data to the readable side's queue.</p>
<h5><code>transformStreamDefaultController.error([reason])</code><span><a class="mark" href="#transformstreamdefaultcontrollererrorreason" id="transformstreamdefaultcontrollererrorreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transformstreamdefaultcontroller_error_reason"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
</ul>
<p>Signals to both the readable and writable side that an error has occurred
while processing the transform data, causing both sides to be abruptly
closed.</p>
<h5><code>transformStreamDefaultController.terminate()</code><span><a class="mark" href="#transformstreamdefaultcontrollerterminate" id="transformstreamdefaultcontrollerterminate">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transformstreamdefaultcontroller_terminate"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><p>Closes the readable side of the transport and causes the writable side
to be abruptly closed with an error.</p>
<h4>Class: <code>ByteLengthQueuingStrategy</code><span><a class="mark" href="#class-bytelengthqueuingstrategy" id="class-bytelengthqueuingstrategy">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_bytelengthqueuingstrategy"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><h5><code>new ByteLengthQueuingStrategy(init)</code><span><a class="mark" href="#new-bytelengthqueuingstrategyinit" id="new-bytelengthqueuingstrategyinit">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_bytelengthqueuingstrategy_init"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>init</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
</li>
</ul>
<h5><code>byteLengthQueuingStrategy.highWaterMark</code><span><a class="mark" href="#bytelengthqueuingstrategyhighwatermark" id="bytelengthqueuingstrategyhighwatermark">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_bytelengthqueuingstrategy_highwatermark"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
<h5><code>byteLengthQueuingStrategy.size</code><span><a class="mark" href="#bytelengthqueuingstrategysize" id="bytelengthqueuingstrategysize">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_bytelengthqueuingstrategy_size"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a><ul>
<li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
</li>
</ul>
<h4>Class: <code>CountQueuingStrategy</code><span><a class="mark" href="#class-countqueuingstrategy" id="class-countqueuingstrategy">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_countqueuingstrategy"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.5.0</td>
<td><p><span>Added in: v16.5.0</span></p>
</td></tr>
</table>
</details>
</div><h5><code>new CountQueuingStrategy(init)</code><span><a class="mark" href="#new-countqueuingstrategyinit" id="new-countqueuingstrategyinit">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_countqueuingstrategy_init"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li><code>init</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
</li>
</ul>
<h5><code>countQueuingStrategy.highWaterMark</code><span><a class="mark" href="#countqueuingstrategyhighwatermark" id="countqueuingstrategyhighwatermark">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_countqueuingstrategy_highwatermark"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
<h5><code>countQueuingStrategy.size</code><span><a class="mark" href="#countqueuingstrategysize" id="countqueuingstrategysize">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_countqueuingstrategy_size"></a></h5>
<div class="api_metadata">
<span>Added in: v16.5.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a><ul>
<li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li>
</ul>
</li>
</ul>
<h4>Class: <code>TextEncoderStream</code><span><a class="mark" href="#class-textencoderstream" id="class-textencoderstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_textencoderstream"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.6.0</td>
<td><p><span>Added in: v16.6.0</span></p>
</td></tr>
</table>
</details>
</div><h5><code>new TextEncoderStream()</code><span><a class="mark" href="#new-textencoderstream" id="new-textencoderstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_textencoderstream"></a></h5>
<div class="api_metadata">
<span>Added in: v16.6.0</span>
</div><p>Creates a new <code>TextEncoderStream</code> instance.</p>
<h5><code>textEncoderStream.encoding</code><span><a class="mark" href="#textencoderstreamencoding" id="textencoderstreamencoding">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textencoderstream_encoding"></a></h5>
<div class="api_metadata">
<span>Added in: v16.6.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>The encoding supported by the <code>TextEncoderStream</code> instance.</p>
<h5><code>textEncoderStream.readable</code><span><a class="mark" href="#textencoderstreamreadable" id="textencoderstreamreadable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textencoderstream_readable"></a></h5>
<div class="api_metadata">
<span>Added in: v16.6.0</span>
</div><ul>
<li>Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li>
</ul>
<h5><code>textEncoderStream.writable</code><span><a class="mark" href="#textencoderstreamwritable" id="textencoderstreamwritable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textencoderstream_writable"></a></h5>
<div class="api_metadata">
<span>Added in: v16.6.0</span>
</div><ul>
<li>Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a></li>
</ul>
<h4>Class: <code>TextDecoderStream</code><span><a class="mark" href="#class-textdecoderstream" id="class-textdecoderstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_textdecoderstream"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v16.6.0</td>
<td><p><span>Added in: v16.6.0</span></p>
</td></tr>
</table>
</details>
</div><h5><code>new TextDecoderStream([encoding[, options]])</code><span><a class="mark" href="#new-textdecoderstreamencoding-options" id="new-textdecoderstreamencoding-options">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_textdecoderstream_encoding_options"></a></h5>
<div class="api_metadata">
<span>Added in: v16.6.0</span>
</div><ul>
<li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Identifies the <code>encoding</code> that this <code>TextDecoder</code> instance
supports. <strong>Default:</strong> <code>'utf-8'</code>.</li>
<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a><ul>
<li><code>fatal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if decoding failures are fatal.</li>
<li><code>ignoreBOM</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, the <code>TextDecoderStream</code> will include the
byte order mark in the decoded result. When <code>false</code>, the byte order mark
will be removed from the output. This option is only used when <code>encoding</code> is
<code>'utf-8'</code>, <code>'utf-16be'</code>, or <code>'utf-16le'</code>. <strong>Default:</strong> <code>false</code>.</li>
</ul>
</li>
</ul>
<p>Creates a new <code>TextDecoderStream</code> instance.</p>
<h5><code>textDecoderStream.encoding</code><span><a class="mark" href="#textdecoderstreamencoding" id="textdecoderstreamencoding">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textdecoderstream_encoding"></a></h5>
<div class="api_metadata">
<span>Added in: v16.6.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li>
</ul>
<p>The encoding supported by the <code>TextDecoderStream</code> instance.</p>
<h5><code>textDecoderStream.fatal</code><span><a class="mark" href="#textdecoderstreamfatal" id="textdecoderstreamfatal">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textdecoderstream_fatal"></a></h5>
<div class="api_metadata">
<span>Added in: v16.6.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
<p>The value will be <code>true</code> if decoding errors result in a <code>TypeError</code> being
thrown.</p>
<h5><code>textDecoderStream.ignoreBOM</code><span><a class="mark" href="#textdecoderstreamignorebom" id="textdecoderstreamignorebom">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textdecoderstream_ignorebom"></a></h5>
<div class="api_metadata">
<span>Added in: v16.6.0</span>
</div><ul>
<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li>
</ul>
<p>The value will be <code>true</code> if the decoding result will include the byte order
mark.</p>
<h5><code>textDecoderStream.readable</code><span><a class="mark" href="#textdecoderstreamreadable" id="textdecoderstreamreadable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textdecoderstream_readable"></a></h5>
<div class="api_metadata">
<span>Added in: v16.6.0</span>
</div><ul>
<li>Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li>
</ul>
<h5><code>textDecoderStream.writable</code><span><a class="mark" href="#textdecoderstreamwritable" id="textdecoderstreamwritable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textdecoderstream_writable"></a></h5>
<div class="api_metadata">
<span>Added in: v16.6.0</span>
</div><ul>
<li>Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a></li>
</ul>
<h4>Class: <code>CompressionStream</code><span><a class="mark" href="#class-compressionstream" id="class-compressionstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_compressionstream"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v17.0.0</td>
<td><p><span>Added in: v17.0.0</span></p>
</td></tr>
</table>
</details>
</div><h5><code>new CompressionStream(format)</code><span><a class="mark" href="#new-compressionstreamformat" id="new-compressionstreamformat">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_compressionstream_format"></a></h5>
<div class="api_metadata">
<span>Added in: v17.0.0</span>
</div><ul>
<li><code>format</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> One of either <code>'deflate'</code> or <code>'gzip'</code>.</li>
</ul>
<h5><code>compressionStream.readable</code><span><a class="mark" href="#compressionstreamreadable" id="compressionstreamreadable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_compressionstream_readable"></a></h5>
<div class="api_metadata">
<span>Added in: v17.0.0</span>
</div><ul>
<li>Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li>
</ul>
<h5><code>compressionStream.writable</code><span><a class="mark" href="#compressionstreamwritable" id="compressionstreamwritable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_compressionstream_writable"></a></h5>
<div class="api_metadata">
<span>Added in: v17.0.0</span>
</div><ul>
<li>Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a></li>
</ul>
<h4>Class: <code>DecompressionStream</code><span><a class="mark" href="#class-decompressionstream" id="class-decompressionstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_decompressionstream"></a></h4>
<div class="api_metadata">
<details class="changelog"><summary>History</summary>
<table>
<tr><th>Version</th><th>Changes</th></tr>
<tr><td>v18.0.0</td>
<td><p>This class is now exposed on the global object.</p>
</td></tr>
<tr><td>v17.0.0</td>
<td><p><span>Added in: v17.0.0</span></p>
</td></tr>
</table>
</details>
</div><h5><code>new DecompressionStream(format)</code><span><a class="mark" href="#new-decompressionstreamformat" id="new-decompressionstreamformat">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_decompressionstream_format"></a></h5>
<div class="api_metadata">
<span>Added in: v17.0.0</span>
</div><ul>
<li><code>format</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> One of either <code>'deflate'</code> or <code>'gzip'</code>.</li>
</ul>
<h5><code>decompressionStream.readable</code><span><a class="mark" href="#decompressionstreamreadable" id="decompressionstreamreadable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_decompressionstream_readable"></a></h5>
<div class="api_metadata">
<span>Added in: v17.0.0</span>
</div><ul>
<li>Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li>
</ul>
<h5><code>decompressionStream.writable</code><span><a class="mark" href="#decompressionstreamwritable" id="decompressionstreamwritable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_decompressionstream_writable"></a></h5>
<div class="api_metadata">
<span>Added in: v17.0.0</span>
</div><ul>
<li>Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a></li>
</ul>
<h4>Utility Consumers<span><a class="mark" href="#utility-consumers" id="utility-consumers">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_utility_consumers"></a></h4>
<div class="api_metadata">
<span>Added in: v16.7.0</span>
</div><p>The utility consumer functions provide common options for consuming
streams.</p>
<p>They are accessed using:</p>
<pre><code class="language-mjs">import {
arrayBuffer,
blob,
buffer,
json,
text,
} from 'node:stream/consumers';
</code></pre>
<pre><code class="language-cjs">const {
arrayBuffer,
blob,
buffer,
json,
text,
} = require('node:stream/consumers');
</code></pre>
<h5><code>streamConsumers.arrayBuffer(stream)</code><span><a class="mark" href="#streamconsumersarraybufferstream" id="streamconsumersarraybufferstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_streamconsumers_arraybuffer_stream"></a></h5>
<div class="api_metadata">
<span>Added in: v16.7.0</span>
</div><ul>
<li><code>stream</code> {ReadableStream|stream.Readable|AsyncIterator}</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with an <code>ArrayBuffer</code> containing the full
contents of the stream.</li>
</ul>
<pre><code class="language-mjs">import { arrayBuffer } from 'node:stream/consumers';
import { Readable } from 'node:stream';
import { TextEncoder } from 'node:util';
const encoder = new TextEncoder();
const dataArray = encoder.encode('hello world from consumers!');
const readable = Readable.from(dataArray);
const data = await arrayBuffer(readable);
console.log(`from readable: ${data.byteLength}`);
</code></pre>
<pre><code class="language-cjs">const { arrayBuffer } = require('node:stream/consumers');
const { Readable } = require('node:stream');
const { TextEncoder } = require('node:util');
const encoder = new TextEncoder();
const dataArray = encoder.encode('hello world from consumers!');
const readable = Readable.from(dataArray);
arrayBuffer(readable).then((data) => {
console.log(`from readable: ${data.byteLength}`);
});
</code></pre>
<h5><code>streamConsumers.blob(stream)</code><span><a class="mark" href="#streamconsumersblobstream" id="streamconsumersblobstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_streamconsumers_blob_stream"></a></h5>
<div class="api_metadata">
<span>Added in: v16.7.0</span>
</div><ul>
<li><code>stream</code> {ReadableStream|stream.Readable|AsyncIterator}</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with a <a href="buffer.html#class-blob" class="type"><Blob></a> containing the full contents
of the stream.</li>
</ul>
<pre><code class="language-mjs">import { blob } from 'node:stream/consumers';
const dataBlob = new Blob(['hello world from consumers!']);
const readable = dataBlob.stream();
const data = await blob(readable);
console.log(`from readable: ${data.size}`);
</code></pre>
<pre><code class="language-cjs">const { blob } = require('node:stream/consumers');
const dataBlob = new Blob(['hello world from consumers!']);
const readable = dataBlob.stream();
blob(readable).then((data) => {
console.log(`from readable: ${data.size}`);
});
</code></pre>
<h5><code>streamConsumers.buffer(stream)</code><span><a class="mark" href="#streamconsumersbufferstream" id="streamconsumersbufferstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_streamconsumers_buffer_stream"></a></h5>
<div class="api_metadata">
<span>Added in: v16.7.0</span>
</div><ul>
<li><code>stream</code> {ReadableStream|stream.Readable|AsyncIterator}</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with a <a href="buffer.html#class-buffer" class="type"><Buffer></a> containing the full
contents of the stream.</li>
</ul>
<pre><code class="language-mjs">import { buffer } from 'node:stream/consumers';
import { Readable } from 'node:stream';
import { Buffer } from 'node:buffer';
const dataBuffer = Buffer.from('hello world from consumers!');
const readable = Readable.from(dataBuffer);
const data = await buffer(readable);
console.log(`from readable: ${data.length}`);
</code></pre>
<pre><code class="language-cjs">const { buffer } = require('node:stream/consumers');
const { Readable } = require('node:stream');
const { Buffer } = require('node:buffer');
const dataBuffer = Buffer.from('hello world from consumers!');
const readable = Readable.from(dataBuffer);
buffer(readable).then((data) => {
console.log(`from readable: ${data.length}`);
});
</code></pre>
<h5><code>streamConsumers.json(stream)</code><span><a class="mark" href="#streamconsumersjsonstream" id="streamconsumersjsonstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_streamconsumers_json_stream"></a></h5>
<div class="api_metadata">
<span>Added in: v16.7.0</span>
</div><ul>
<li><code>stream</code> {ReadableStream|stream.Readable|AsyncIterator}</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with the contents of the stream parsed as a
UTF-8 encoded string that is then passed through <code>JSON.parse()</code>.</li>
</ul>
<pre><code class="language-mjs">import { json } from 'node:stream/consumers';
import { Readable } from 'node:stream';
const items = Array.from(
{
length: 100,
},
() => ({
message: 'hello world from consumers!',
}),
);
const readable = Readable.from(JSON.stringify(items));
const data = await json(readable);
console.log(`from readable: ${data.length}`);
</code></pre>
<pre><code class="language-cjs">const { json } = require('node:stream/consumers');
const { Readable } = require('node:stream');
const items = Array.from(
{
length: 100,
},
() => ({
message: 'hello world from consumers!',
}),
);
const readable = Readable.from(JSON.stringify(items));
json(readable).then((data) => {
console.log(`from readable: ${data.length}`);
});
</code></pre>
<h5><code>streamConsumers.text(stream)</code><span><a class="mark" href="#streamconsumerstextstream" id="streamconsumerstextstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_streamconsumers_text_stream"></a></h5>
<div class="api_metadata">
<span>Added in: v16.7.0</span>
</div><ul>
<li><code>stream</code> {ReadableStream|stream.Readable|AsyncIterator}</li>
<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with the contents of the stream parsed as a
UTF-8 encoded string.</li>
</ul>
<pre><code class="language-mjs">import { text } from 'node:stream/consumers';
import { Readable } from 'node:stream';
const readable = Readable.from('Hello world from consumers!');
const data = await text(readable);
console.log(`from readable: ${data.length}`);
</code></pre>
<pre><code class="language-cjs">const { text } = require('node:stream/consumers');
const { Readable } = require('node:stream');
const readable = Readable.from('Hello world from consumers!');
text(readable).then((data) => {
console.log(`from readable: ${data.length}`);
});
</code></pre>
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