chunkBlob.js

const defaultChunkSize = 1 * 1024 * 1024; // 1 MB
const chunkBlob = ({chunkSize = defaultChunkSize, blob}) => {
  function* go(offset, chunkId) {
    if(offset < blob.size) {
      const nextOffset = offset + chunkSize + 1;
      yield {
        chunkId,
        chunk: file.slice(offset, nextOffset)
      };
      yield* go(nextOffset, chunkId + 1);
    }
  }
  return go(0, 0);
}

example.js

const uploadChunk = ({chunk, chunkId}) =>
  $.ajax({
    // do the request here
  })

async function example(file) {
  Promise.all(chunkBlob(file).map(async function({chunk, chunkId}) {
    const chunkArrayBuffer = await readBlobAsync(chunk);
    return uploadChunk({chunk: chunkArrayBuffer, chunkId});
  }));
}

readBlobAsync.js

const readBlobAsync = (blob) => 
  new Promise((resolve, reject) => {
    let reader = new FileReader();
    reader.onload = () => resolve(reader.result)
    reader.onerror = reject;
    reader.readAsArrayBuffer(blob);
  })