Source: misc/progress.js

/**
 * @file
 * Progress bar.
 */

(function ($, Drupal) {

  'use strict';

  /**
   * Theme function for the progress bar.
   *
   * @param {string} id
   *   The id for the progress bar.
   *
   * @return {string}
   *   The HTML for the progress bar.
   */
  Drupal.theme.progressBar = function (id) {
    return '<div id="' + id + '" class="progress" aria-live="polite">' +
      '<div class="progress__label">&nbsp;</div>' +
      '<div class="progress__track"><div class="progress__bar"></div></div>' +
      '<div class="progress__percentage"></div>' +
      '<div class="progress__description">&nbsp;</div>' +
      '</div>';
  };

  /**
   * A progressbar object. Initialized with the given id. Must be inserted into
   * the DOM afterwards through progressBar.element.
   *
   * Method is the function which will perform the HTTP request to get the
   * progress bar state. Either "GET" or "POST".
   *
   * @example
   * pb = new Drupal.ProgressBar('myProgressBar');
   * some_element.appendChild(pb.element);
   *
   * @constructor
   *
   * @param {string} id
   *   The id for the progressbar.
   * @param {function} updateCallback
   *   Callback to run on update.
   * @param {string} method
   *   HTTP method to use.
   * @param {function} errorCallback
   *   Callback to call on error.
   */
  Drupal.ProgressBar = function (id, updateCallback, method, errorCallback) {
    this.id = id;
    this.method = method || 'GET';
    this.updateCallback = updateCallback;
    this.errorCallback = errorCallback;

    // The WAI-ARIA setting aria-live="polite" will announce changes after
    // users
    // have completed their current activity and not interrupt the screen
    // reader.
    this.element = $(Drupal.theme('progressBar', id));
  };

  $.extend(Drupal.ProgressBar.prototype, /** @lends Drupal.ProgressBar# */{

    /**
     * Set the percentage and status message for the progressbar.
     *
     * @param {number} percentage
     *   The progress percentage.
     * @param {string} message
     *   The message to show the user.
     * @param {string} label
     *   The text for the progressbar label.
     */
    setProgress: function (percentage, message, label) {
      if (percentage >= 0 && percentage <= 100) {
        $(this.element).find('div.progress__bar').css('width', percentage + '%');
        $(this.element).find('div.progress__percentage').html(percentage + '%');
      }
      $('div.progress__description', this.element).html(message);
      $('div.progress__label', this.element).html(label);
      if (this.updateCallback) {
        this.updateCallback(percentage, message, this);
      }
    },

    /**
     * Start monitoring progress via Ajax.
     *
     * @param {string} uri
     *   The URI to use for monitoring.
     * @param {number} delay
     *   The delay for calling the monitoring URI.
     */
    startMonitoring: function (uri, delay) {
      this.delay = delay;
      this.uri = uri;
      this.sendPing();
    },

    /**
     * Stop monitoring progress via Ajax.
     */
    stopMonitoring: function () {
      clearTimeout(this.timer);
      // This allows monitoring to be stopped from within the callback.
      this.uri = null;
    },

    /**
     * Request progress data from server.
     */
    sendPing: function () {
      if (this.timer) {
        clearTimeout(this.timer);
      }
      if (this.uri) {
        var pb = this;
        // When doing a post request, you need non-null data. Otherwise a
        // HTTP 411 or HTTP 406 (with Apache mod_security) error may result.
        var uri = this.uri;
        if (uri.indexOf('?') === -1) {
          uri += '?';
        }
        else {
          uri += '&';
        }
        uri += '_format=json';
        $.ajax({
          type: this.method,
          url: uri,
          data: '',
          dataType: 'json',
          success: function (progress) {
            // Display errors.
            if (progress.status === 0) {
              pb.displayError(progress.data);
              return;
            }
            // Update display.
            pb.setProgress(progress.percentage, progress.message, progress.label);
            // Schedule next timer.
            pb.timer = setTimeout(function () { pb.sendPing(); }, pb.delay);
          },
          error: function (xmlhttp) {
            var e = new Drupal.AjaxError(xmlhttp, pb.uri);
            pb.displayError('<pre>' + e.message + '</pre>');
          }
        });
      }
    },

    /**
     * Display errors on the page.
     *
     * @param {string} string
     *   The error message to show the user.
     */
    displayError: function (string) {
      var error = $('<div class="messages messages--error"></div>').html(string);
      $(this.element).before(error).hide();

      if (this.errorCallback) {
        this.errorCallback(this);
      }
    }
  });

})(jQuery, Drupal);