The respond() method of the ReadableStreamBYOBRequest interface is used to signal to the associated readable byte stream that the specified number of bytes were written into the ReadableStreamBYOBRequest.view.

After this method is called, the view will be transferred and no longer modifiable.

bytesWritten

The number of bytes written into ReadableStreamBYOBRequest.view.

None (undefined).

TypeError

The request does not have an associated ReadableByteStreamController or the view buffer is not detached/cannot be transferred into.

The code below is taken from the live examples in Using readable byte stream.

The method is called by an underlying byte source as part of making a zero-copy transfer of data to fulfill a pending read request from a consumer. The underlying source first writes data into the ReadableStreamBYOBRequest.view and then calls this respond() method to indicate how much data was copied into the buffer, and cause the data to be transferred to the reader.

The code below shows this case using a hypothetical readInto() method to copy data into the view:

const v = controller.byobRequest.view;
bytesRead = socket.readInto(v.buffer, v.byteOffset, v.byteLength);
controller.byobRequest.respond(bytesRead);

After the operation the byobRequest.view is detached and the request should be discarded.

• Using readable byte stream