Download (multiple) pdf files with ajax and add to a zip file in browser

ajax-zip.js

var JSZip = require('jszip'),
    Q = require('q');

var downloadFile = function(url) {
  var defer = Q.defer();
  var xhr = new XMLHttpRequest();
  xhr.open('GET', url, true);
  xhr.responseType = 'arraybuffer';
  xhr.onreadystatechange = function() {
    if (xhr.readyState === 4) {
      if (xhr.status < 400) {
        defer.resolve(xhr.response);
      } else {
        defer.reject(new Error("Failed to load file from server"));
      }   
    }   
  };  
  xhr.send();

  return defer.promise;
};

var files = [{filename: 'foo.pdf', url: '/files/foo.pdf'}, {filename: 'bar.pdf', url: '/files/bar.pdf'}],
    zip = new JSZip();

files.reduce(function(p, o) {
  return p.then(function() {
    return downloadFile(o.url).then(function(arrayBuffer) {
      zip.file(o.filename, arrayBuffer);
    });
  })
}, Q()).then(function() {
  var link = document.getElementById('download-link'),
      blob = zip.generate({type:"blob"}),
  link.download = 'myzip.zip';
  link.href = window.URL.createObjectURL(blob);
});

Am i right in thinking that this streams the xhr arraybuffer into the zip "blob"? Have you thought of anyway to download in parallel, I would think you would run into browser caps without fileAPI.

Great gist!

Does this work on IE9+?. I tried to download multiple pdf files from web with JSZip using ajax call but it does'nt work on IE11. Same code runs on Chrome and Firefox without any issue .

This downloads a terminal and no pdf