ReadableByteStreamController: byobRequest property

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Note: This feature is available in Web Workers.

The byobRequest read-only property of the ReadableByteStreamController interface returns the current BYOB request, or null if there are no pending requests.

An underlying byte source should check this property, and use it to write data to the stream if it exists (rather than using ReadableByteStreamController.enqueue()). This will result in an efficient zero-byte transfer of the data to the consumer.

Value

A ReadableStreamBYOBRequest object instance, or null.

Examples

The example in Using readable byte streams > Creating a readable socket push byte stream shows how you use a byobRequest to transfer data (if it exists), or otherwise copy the data to the stream's internal queues using ReadableByteStreamController.enqueue().

The relevant code is reproduced below. If the byobRequest exists, data is read into controller.byobRequest.view, and then ReadableStreamBYOBRequest.respond() is called to signal the amount of data that is ready to transfer.

js
if (controller.byobRequest) {
  const v = controller.byobRequest.view;
  bytesRead = socket.readInto(v.buffer, v.byteOffset, v.byteLength);
  if (bytesRead === 0) {
    controller.close();
  }
  controller.byobRequest.respond(bytesRead);
} else {
  // Write to data using enqueue().
}

Specifications

Specification
Streams
# ref-for-rbs-controller-byob-request②

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
byobRequest

Legend

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Full support
Full support
No support
No support

See also