Quick example of using fetch to parse a chunked response

fetch-chunked.js

var chunkedUrl = 'https://jigsaw.w3.org/HTTP/ChunkedScript';
fetch(chunkedUrl)
  .then(processChunkedResponse)
  .then(onChunkedResponseComplete)
  .catch(onChunkedResponseError)
  ;

function onChunkedResponseComplete(result) {
  console.log('-----------all done!----------');
  console.log(result);
}

function onChunkedResponseError(err) {
  console.error(err)
}

function processChunkedResponse(response) {
  var text = '';
  var reader = response.body.getReader()
  var decoder = new TextDecoder();
  
  return readChunk();

  function readChunk() {
    return reader.read().then(appendChunks);
  }

  function appendChunks(result) {
    var chunk = decoder.decode(result.value || new Uint8Array, {stream: !result.done});
    console.log('got chunk of', chunk.length, 'bytes')
    console.log('---------chunk--------');
    console.log(chunk);
    text += chunk;
    console.log('text so far is', text.length, 'bytes\n');
    if (result.done) {
      console.log('returning')
      return text;
    } else {
      console.log('recursing')
      return readChunk();
    }
  }
}

response.txt

got chunk of 32768 bytes
text so far is 32768 bytes

recursing
got chunk of 32768 bytes
---------chunk--------
<chunk 1 here>
text so far is 65536 bytes

recursing
got chunk of 6664 bytes
---------chunk--------
<chunk 2 here>
text so far is 72200 bytes

recursing
got chunk of 0 bytes
---------chunk--------

text so far is 72200 bytes

returning
-----------all done!----------
This output will be chunked encoded by the server, if your client is HTTP/1.1
<snip>