ReadableStreamDefaultController.enqueue()

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This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The enqueue() method of the ReadableStreamDefaultController interface enqueues a given chunk in the associated stream.

Syntax

readableStreamDefaultControllerInstance.enqueue(chunk);

Parameters

chunk
The chunk to enqueue.

Return value

Void.

Exceptions

TypeError
The source object is not a ReadableStreamDefaultController.

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 — see controller.enqueue(string). A cancel() function is also provided to stop the generation if ReadableStream.cancel() is called for any reason.

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 'enqueue()' in that specification.
Living Standard Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic support
Experimental
Chrome ? Edge ? Firefox ? IE ? Opera ? Safari ? WebView Android ? Chrome Android ? Edge Mobile ? Firefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android ?

Legend

Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.

Document Tags and Contributors

Contributors to this page: connorshea, chrisdavidmills
Last updated by: connorshea,