/Web APIs

ReadableByteStreamController: byobRequest property

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.


A ReadableStreamBYOBRequest object instance, or null.


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.


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


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
byobRequest 89 89 102 No 75 No 89 89 102 63 No 15.0

See also

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