force-download.js

function setupDownload() {
    // quick test to check if download is available on anchors (fake Modernizr implementation)
    var anchor = document.createElement("A");
    var Modernizr = { adownload: "download" in anchor };
    delete anchor;

    if (Modernizr.adownload) {
      var downloads = document.querySelectorAll("a[download]");

      for (var i = 0; i < downloads.length; i++) {
        downloads[i].addEventListener("click", function(event) {
          event.preventDefault();

          var url = event.currentTarget.href;
          var filename = event.currentTarget.download;
          var mimetype = event.currentTarget.dataset.mimetype;

          // download(url, filename, mimetype);

          var x = new XMLHttpRequest();
          x.open("GET", url, true);
          x.responseType = "blob";
          x.onload = function(e) {
            download(x.response, filename, mimetype);
          };
          x.send();
        });
      }
    }
  }