The ReadableStreamDefaultController
interface of the Streams API represents a controller allowing control of a ReadableStream
's state and internal queue. Default controllers are for streams that are not byte streams.
The ReadableStreamDefaultController
interface of the Streams API represents a controller allowing control of a ReadableStream
's state and internal queue. Default controllers are for streams that are not byte streams.
None. ReadableStreamDefaultController
instances are created automatically during ReadableStream
construction.
ReadableStreamDefaultController.desiredSize
Read only
Returns the desired size required to fill the stream's internal queue.
ReadableStreamDefaultController.close()
Closes the associated stream.
ReadableStreamDefaultController.enqueue()
Enqueues a given chunk in the associated stream.
ReadableStreamDefaultController.error()
Causes any future interactions with the associated stream to error.
In the following simple example, a custom ReadableStream
is created using a constructor (see our Simple random stream example for the full code). The start()
function generates a random string of text every second and enqueues it into the stream. A cancel()
function is also provided to stop the generation if ReadableStream.cancel()
is called for any reason.
Note that a ReadableStreamDefaultController
object is provided as the parameter of the start()
and pull()
functions.
When a button is pressed, the generation is stopped, the stream is closed using ReadableStreamDefaultController.close()
, and another function is run, which reads the data back out of the stream.
js
let interval; const stream = new ReadableStream({ start(controller) { interval = setInterval(() => { let string = randomChars(); // Add the string to the stream controller.enqueue(string); // show it on the screen let listItem = document.createElement("li"); listItem.textContent = string; list1.appendChild(listItem); }, 1000); button.addEventListener("click", () => { clearInterval(interval); fetchStream(); controller.close(); }); }, pull(controller) { // We don't really need a pull in this example }, cancel() { // This is called if the reader cancels, // so we should stop generating strings clearInterval(interval); }, });
Specification |
---|
Streams Standard # rs-default-controller-class |
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
ReadableStreamDefaultController |
≤80 | 80 | 65 | No | 67 | ≤13.1 | 80 | 80 | 65 | 57 | ≤13.4 | 13.0 |
close |
≤80 | 80 | 65 | No | 67 | ≤13.1 | 80 | 80 | 65 | 57 | ≤13.4 | 13.0 |
desiredSize |
≤80 | 80 | 65 | No | 67 | ≤13.1 | 80 | 80 | 65 | 57 | ≤13.4 | 13.0 |
enqueue |
≤80 | 80 | 65 | No | 67 | ≤13.1 | 80 | 80 | 65 | 57 | ≤13.4 | 13.0 |
error |
≤80 | 80 | 65 | No | 67 | ≤13.1 | 80 | 80 | 65 | 57 | ≤13.4 | 13.0 |
ReadableStream
© 2005–2023 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/ReadableStreamDefaultController