ReadableStreamDefaultController.enqueue()

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

Syntax

readableStreamDefaultController.enqueue(chunk);

Parameters

chunk

The chunk to enqueue.

Return value

undefined.

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

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
enqueue
89
89
65
No
75
No
89
89
65
63
No
15.0

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https://developer.mozilla.org/en-US/docs/Web/API/ReadableStreamDefaultController/enqueue