keepAwake.js

/**
 * Keeps devices from falling asleep or turning off their displays while
 * recording data.
 * @class KeepAwake
 */
(function(KeepAwake, undefined) {
  /**
   * Formats a string with given mimeType and data for a src value in a source
   * element for a video.
   *
   * @private
   * @param {string} mimeType The mime type.
   * @param {string} base64 The base 64 data.
   * @return {string} THe formatted string.
   */
  function base64(mimeType, base64) {
    return 'data:' + mimeType + ';base64,' + base64;
  };

  // Create video to play on loop in order to keep device awake.
  const video = document.createElement('video');
  video.loop = true;
  document.body.appendChild(video);

  /**
   * Add data to for video to play.
   *
   * @param {Element} element The parent video element to attach the source to.
   * @param {string} type The mimeType of the source.
   * @param {string} dataURI The src value.
   */
  function addSourceToVideo(element, type, dataURI) {
    const source = document.createElement('source');
    source.src = dataURI;
    source.type = 'video/' + type;
    element.appendChild(source);
  }

  addSourceToVideo(
      video, 'webm',
      base64(
          'video/webm',
          'GkXfo0AgQoaBAUL3gQFC8oEEQvOBCEKCQAR3ZWJtQoeBAkKFgQIYU4BnQI0VSalmQC' +
              'gq17FAAw9CQE2AQAZ3aGFtbXlXQUAGd2hhbW15RIlACECPQAAAAAAAFlSua0Ax' +
              'rkAu14EBY8WBAZyBACK1nEADdW5khkAFVl9WUDglhohAA1ZQOIOBAeBABrCBCL' +
              'qBCB9DtnVAIueBAKNAHIEAAIAwAQCdASoIAAgAAUAmJaQAA3AA/vz0AAA='));
  addSourceToVideo(
      video, 'mp4',
      base64(
          'video/mp4',
          'AAAAHGZ0eXBpc29tAAACAGlzb21pc28ybXA0MQAAAAhmcmVlAAAAG21kYXQAAAGzAB' +
              'AHAAABthADAowdbb9/AAAC6W1vb3YAAABsbXZoZAAAAAB8JbCAfCWwgAAAA+gA' +
              'AAAAAAEAAAEAAAAAAAAAAAAAAAABAAAAAAAAAAAAAAAAAAAAAQAAAAAAAAAAAA' +
              'AAAAAAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAIAAAIVdHJhawAA' +
              'AFx0a2hkAAAAD3wlsIB8JbCAAAAAAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA' +
              'ABAAAAAAAAAAAAAAAAAAAAAQAAAAAAAAAAAAAAAAAAQAAAAAAIAAAACAAAAAAB' +
              'sW1kaWEAAAAgbWRoZAAAAAB8JbCAfCWwgAAAA+gAAAAAVcQAAAAAAC1oZGxyAA' +
              'AAAAAAAAB2aWRlAAAAAAAAAAAAAAAAVmlkZW9IYW5kbGVyAAAAAVxtaW5mAAAA' +
              'FHZtaGQAAAABAAAAAAAAAAAAAAAkZGluZgAAABxkcmVmAAAAAAAAAAEAAAAMdX' +
              'JsIAAAAAEAAAEcc3RibAAAALhzdHNkAAAAAAAAAAEAAACobXA0dgAAAAAAAAAB' +
              'AAAAAAAAAAAAAAAAAAAAAAAIAAgASAAAAEgAAAAAAAAAAQAAAAAAAAAAAAAAAA' +
              'AAAAAAAAAAAAAAAAAAAAAAAAAAABj//wAAAFJlc2RzAAAAAANEAAEABDwgEQAA' +
              'AAADDUAAAAAABS0AAAGwAQAAAbWJEwAAAQAAAAEgAMSNiB9FAEQBFGMAAAGyTG' +
              'F2YzUyLjg3LjQGAQIAAAAYc3R0cwAAAAAAAAABAAAAAQAAAAAAAAAcc3RzYwAA' +
              'AAAAAAABAAAAAQAAAAEAAAABAAAAFHN0c3oAAAAAAAAAEwAAAAEAAAAUc3Rjbw' +
              'AAAAAAAAABAAAALAAAAGB1ZHRhAAAAWG1ldGEAAAAAAAAAIWhkbHIAAAAAAAAA' +
              'AG1kaXJhcHBsAAAAAAAAAAAAAAAAK2lsc3QAAAAjqXRvbwAAABtkYXRhAAAAAQ' +
              'AAAABMYXZmNTIuNzguMw=='));

  /**
   * Set method for keeping device awake.
   *
   * @public
   * @param {string} mode The method to use.
   */
  KeepAwake.keepAwakeSetting = function(mode) {
    keepAwakeMode = mode;
  };
  /**
   * Enable/Disable keeping device awake.
   * @TODO: Fix pageload leak.
   *
   * @public
   * @param {boolean} setting Enable or Disable.
   */
  KeepAwake.keepAwake = function(setting) {
    try {
      if (keepAwakeMode == 'video') {
        // Play a video to keep the device awake. (Chrome)
        setting ? video.play() : video.pause();
      } else if (keepAwakeMode == 'pageload') {
        // Every 30s change the page then cancel page change. (Safari)
        setInterval(function() {
          window.location.href = '/fake/page';
          window.setTimeout(window.stop);
        }, 30000);
      }
    } catch (err) {
      console.error(err);
    }
  };
}(window.KeepAwake = window.KeepAwake || {}));