The enqueue() method of the ReadableByteStreamController interface enqueues a given chunk on the associated readable byte stream (the chunk is copied into the stream's internal queues).

This should only be used to transfer data to the queue when byobRequest is null.

chunk

The chunk to enqueue.

None (undefined).

TypeError

Thrown if the source object is not a ReadableByteStreamController, or the stream cannot be read for some other reason, or the chunk is not an object, or the chunk's internal array buffer is non-existent, zero-length, or detached. It is also thrown if the stream has been closed.

The example in Using readable byte streams > Creating a readable socket push byte stream shows how you can use enqueue() to copy data to the stream if there is no outstanding byobRequest. If there is a byobRequest then it should be used!

The code below shows data being read into an ArrayBuffer using a "hypothetical" socket.readInto() method and then enqueued (but only if data was actually copied):

const buffer = new ArrayBuffer(DEFAULT_CHUNK_SIZE);
bytesRead = socket.readInto(buffer, 0, DEFAULT_CHUNK_SIZE);
if (bytesRead === 0) {
  controller.close();
} else {
  controller.enqueue(new Uint8Array(buffer, 0, bytesRead));
}

• Using readable byte streams
• ReadableByteStreamController