This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The ReadableStream
interface of the Streams API represents a readable stream of byte data. The Fetch API offers a concrete instance of a ReadableStream
through the body
property of a Response
object.
Constructor
ReadableStream()
- Creates and returns a readable stream object from the given handlers.
-
Properties
ReadableStream.locked
Read only- The
locked
getter returns whether or not the readable stream is locked to a reader.
Methods
ReadableStream.cancel()
- Cancels the stream, signaling a loss of interest in the stream by a consumer. The supplied reason argument will be given to the underlying source, which may or may not use it.
ReadableStream.getReader()
- Creates a reader and locks the stream to it. While the stream is locked, no other reader can be acquired until this one is released.
ReadableStream.pipeThrough()
- Provides a chainable way of piping the current stream through a transform stream or any other writable/readable pair.
ReadableStream.pipeTo()
- Pipes the current ReadableStream to a given
WritableStream
and returns a promise that fulfills when the piping process completes successfully, or rejects if any errors were encountered. ReadableStream.tee()
- The
tee
method tees this readable stream, returning a two-element array containing the two resulting branches as newReadableStream
instances.
Examples
In the following example, an artifical Response
is created to stream HTML fragments fetched from another resource to the browser.
It demonstrates the usage of a ReadableStream
in combination with a Uint8Array
.
fetch("https://www.example.org/").then((response) => { const reader = response.body.getReader(); const stream = new ReadableStream({ start(controller) { // The following function handles each data chunk function push() { // "done" is a Boolean and value a "Uint8Array" return reader.read().then(({ done, value }) => { // Is there no more data to read? if (done) { // Tell the browser that we have finished sending data controller.close(); return; } // Get the data and send it to the browser via the controller controller.enqueue(value); }).then(push); }; push(); } }); return new Response(stream, { headers: { "Content-Type": "text/html" } }); });
Specifications
Specification | Status | Comment |
---|---|---|
Streams The definition of 'ReadableStream' in that specification. |
Living Standard | Initial definition |
Browser Compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support |
43.0 |
No support[1] | ? |
39 |
? |
pipeThrough and pipeTo methods |
59.0 | No support[1] | ? | 46 | ? |
Feature | Android Webview | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | 43 | 43 | No support[1] | ? | 39 | ? |
pipeThrough and pipeTo methods |
59 | 59 | No support[1] | ? | 46 | ? |
[1] Readable streams are currently enabled in Firefox, but hidden behind the dom.streams.enabled
and javascript.options.streams
prefs.