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.
Constructor
None. ReadableStreamDefaultController
instances are created automatically during ReadableStream
construction.
Properties
ReadableStreamDefaultController.desiredSize
Read only- Returns the desired size required to fill the stream's internal queue.
Methods
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.
Examples
In the following simple example, a custom ReadableStream
is created using a constructor (see our [[../../../../../../mdn.github.io/dom-examples/streams/simple-random-stream/index|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.
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', function() {
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);
}
});
Specifications
Specification | Status | Comment |
StreamsThe definition of 'ReadableStreamDefaultController' in that specification. | Living Standard | Initial definition |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Update compatibility data on GitHub
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Chrome
Full support 52 |
Edge
Full support ≤79 |
Firefox Full support 65 Full support 65 Full support 57 Disabled' From version 57: this feature is behind the |
IE
No support No |
Opera
Full support 39 |
Safari
? |
WebView Android
Full support 52 |
Chrome Android
Full support 52 |
Firefox Android Full support 65 Full support 65 Full support 57 Disabled' From version 57: this feature is behind the |
Opera Android
Full support 41 |
Safari iOS
? |
Samsung Internet Android
Full support 6.0 |
Chrome
? |
Edge
? |
Firefox Full support 65 Full support 65 Full support 57 Disabled' From version 57: this feature is behind the |
IE
No support No |
Opera
? |
Safari
? |
WebView Android
? |
Chrome Android
? |
Firefox Android Full support 65 Full support 65 Full support 57 Disabled' From version 57: this feature is behind the |
Opera Android
? |
Safari iOS
? |
Samsung Internet Android
? | |
Chrome
? |
Edge
? |
Firefox Full support 65 Full support 65 Full support 57 Disabled' From version 57: this feature is behind the |
IE
No support No |
Opera
? |
Safari
? |
WebView Android
? |
Chrome Android
? |
Firefox Android Full support 65 Full support 65 Full support 57 Disabled' From version 57: this feature is behind the |
Opera Android
? |
Safari iOS
? |
Samsung Internet Android
? | |
Chrome
? |
Edge
? |
Firefox Full support 65 Full support 65 Full support 57 Disabled' From version 57: this feature is behind the |
IE
No support No |
Opera
? |
Safari
? |
WebView Android
? |
Chrome Android
? |
Firefox Android Full support 65 Full support 65 Full support 57 Disabled' From version 57: this feature is behind the |
Opera Android
? |
Safari iOS
? |
Samsung Internet Android
? | |
Chrome
? |
Edge
? |
Firefox Full support 65 Full support 65 Full support 57 Disabled' From version 57: this feature is behind the |
IE
No support No |
Opera
? |
Safari
? |
WebView Android
? |
Chrome Android
? |
Firefox Android Full support 65 Full support 65 Full support 57 Disabled' From version 57: this feature is behind the |
Opera Android
? |
Safari iOS
? |
Samsung Internet Android
? |
Legend
- Full support
- Full support
- No support
- No support
- Compatibility unknown
- Compatibility unknown
- Experimental. Expect behavior to change in the future.'
- Experimental. Expect behavior to change in the future.
- User must explicitly enable this feature.'
- User must explicitly enable this feature.
ReadableStreamDefaultController by Mozilla Contributors is licensed under CC-BY-SA 2.5.