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 duringReadableStream
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 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 |
---|---|---|
Streams The definition of 'ReadableStreamDefaultController' in that specification. |
Living Standard | Initial definition |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
ReadableStreamDefaultController | Chrome Full support 52 | Edge Full support ≤79 | Firefox
Full support
65
| IE ? | Opera Full support 39 | Safari ? | WebView Android Full support 52 | Chrome Android Full support 52 | Firefox Android
Full support
65
| Opera Android Full support 41 | Safari iOS ? | Samsung Internet Android Full support 6.0 |
close | Chrome ? | Edge ? | Firefox
Full support
65
| IE ? | Opera ? | Safari ? | WebView Android ? | Chrome Android ? | Firefox Android
Full support
65
| Opera Android ? | Safari iOS ? | Samsung Internet Android ? |
desiredSize | Chrome ? | Edge ? | Firefox
Full support
65
| IE ? | Opera ? | Safari ? | WebView Android ? | Chrome Android ? | Firefox Android
Full support
65
| Opera Android ? | Safari iOS ? | Samsung Internet Android ? |
enqueue | Chrome ? | Edge ? | Firefox
Full support
65
| IE ? | Opera ? | Safari ? | WebView Android ? | Chrome Android ? | Firefox Android
Full support
65
| Opera Android ? | Safari iOS ? | Samsung Internet Android ? |
error | Chrome ? | Edge ? | Firefox
Full support
65
| IE ? | Opera ? | Safari ? | WebView Android ? | Chrome Android ? | Firefox Android
Full support
65
| Opera Android ? | Safari iOS ? | Samsung Internet Android ? |
Legend
- Full support
- Full 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.