切分上传

function upload(blobOrFile) {
  var xhr = new XMLHttpRequest();
  xhr.open('POST', '/server', true);
  xhr.onload = function(e) { ... };
  xhr.send(blobOrFile);
}

document.querySelector('input[type="file"]').addEventListener('change', function(e) {
  var blob = this.files[0];

  const BYTES\_PER\_CHUNK = 1024 \* 1024; // 1MB chunk sizes.
  const SIZE = blob.size;

  var start = 0;
  var end = BYTES\_PER\_CHUNK;

  while(start \< SIZE) {
    upload(blob.slice(start, end));

    start = end;
    end = start + BYTES\_PER\_CHUNK;
  }
}, false);

})();