Need help with streams!
How do I find the byte size of a chunk, or the total bytes written/read so far?
I need to understand the total byte-size of the stream once it's flushed (it's for https://github.com/w3c/navigation-timing/issues/124).

Maybe Mattias Buelens?

The idiomatic solution would be to pipe it through a TransformStream that adds up the byteLength of each chunk.

let totalBytes = 0;
const transform = new TransformStream({
  transform(chunk, controller) {
      totalBytes += chunk.byteLength;
      controller.enqueue(chunk);
  },
  flush() {
      console.log(`Downloaded ${totalBytes} bytes`);
  }
});

Ah, here it is: https://webidl.spec.whatwg.org/#buffersource-byte-length