Response: arrayBuffer() method

The arrayBuffer() method of the {{domxref("Response")}} interface takes a {{domxref("Response")}} stream and reads it to completion. It returns a promise that resolves with an {{jsxref("ArrayBuffer")}}.

Syntax

js-nolint

arrayBuffer()

Parameters

None.

Return value

A promise that resolves with an {{jsxref("ArrayBuffer")}}.

Exceptions

AbortError {{domxref("DOMException")}}
- : The request was aborted.
{{jsxref("TypeError")}}
- : Thrown for one of the following reasons:
  - The response body is disturbed or locked.
  - There was an error decoding the body content (for example, because the {{httpheader("Content-Encoding")}} header is incorrect).
{{jsxref("RangeError")}}
- : Thrown if there is a problem creating the associated ArrayBuffer (for example, if the data size is too large).

Examples

Playing music

In our fetch array buffer live, we have a Play button. When pressed, the getData() function is run. Note that before playing full audio file will be downloaded. If you need to play ogg during downloading (stream it) - consider {{domxref("HTMLAudioElement")}}:

new Audio("music.ogg").play();

In getData() we create a new request using the {{domxref("Request.Request","Request()")}} constructor, then use it to fetch an OGG music track. We also use {{domxref("BaseAudioContext/createBufferSource", "AudioContext.createBufferSource")}} to create an audio buffer source. When the fetch is successful, we read an {{jsxref("ArrayBuffer")}} out of the response using arrayBuffer(), decode the audio data using {{domxref("BaseAudioContext/decodeAudioData", "AudioContext.decodeAudioData()")}}, set the decoded data as the audio buffer source's buffer (source.buffer), then connect the source up to the {{domxref("BaseAudioContext/destination", "AudioContext.destination")}}.

Once getData() has finished running, we start the audio source playing with start(0), then disable the play button so it can't be clicked again when it is already playing (this would cause an error.)

function getData() {
  const audioCtx = new AudioContext();

  return fetch("viper.ogg")
    .then((response) => {
      if (!response.ok) {
        throw new Error(`HTTP error, status = ${response.status}`);
      }
      return response.arrayBuffer();
    })
    .then((buffer) => audioCtx.decodeAudioData(buffer))
    .then((decodedData) => {
      const source = new AudioBufferSourceNode(audioCtx);
      source.buffer = decodedData;
      source.connect(audioCtx.destination);
      return source;
    });
}

// wire up buttons to stop and play audio

play.onclick = () => {
  getData().then((source) => {
    source.start(0);
    play.setAttribute("disabled", "disabled");
  });
};

Reading files

The {{domxref("Response.Response","Response()")}} constructor accepts {{domxref("File")}}s and {{domxref("Blob")}}s, so it may be used to read a {{domxref("File")}} into other formats.

html

<input type="file" />

function readFile(file) {
  return new Response(file).arrayBuffer();
}

document
  .querySelector("input[type=file]")
  .addEventListener("change", (event) => {
    const file = event.target.files[0];
    const buffer = readFile(file);
  });