The byteLength read-only property of the EncodedAudioChunk interface returns the length in bytes of the encoded audio data.

An integer.

In the following example the byteLength is printed to the console.

const init = {
  type: "key",
  data: audioBuffer,
  timestamp: 23000000,
  duration: 2000000,
};
chunk = EncodedAudioChunk(init);

console.log(chunk.byteLength); //352800