unload.js

// Adds 'unloading' class to `html` tag when navigating away from the page
//
// Make sure downloads open in another page with target="_blank"
// "beforeunload" is fired any time a link is clicked.
// If the link points to a file to download, the user won't be actually
// leaving the page, but beforeunload will still have fired.

(function () {
  var unload = {};
  unload.init = function () {
    // Cache html element
    unload.$html = $(document.documentElement);

    // Attach event
    $(window).on('beforeunload', unload.unloading);
  }

  unload.unloading = function (e) {
    unload.$html.addClass('unloading');

    // Set fallback
    setTimeout(unload.failed, 5000);
  }

  // Useful if the user comes back, the loading fails, or it takes way too long
  unload.failed = function () {
    unload.$html.removeClass('unloading');
  }

  // Set this whole thing up on DOMready
  $(unload.init);
  return unload;
})();