YouTube Wait for Me - Pause and Start Player in Background Tabs

Pause the video in YouTube tabs opened in the background, play on activation 2016-08-18 (I know, it doesn't pause fast enough)

You will need to install an extension such as Tampermonkey, Greasemonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey to install this script.

You will need to install an extension such as Tampermonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Userscripts to install this script.

You will need to install an extension such as Tampermonkey to install this script.

You will need to install a user script manager extension to install this script.

(I already have a user script manager, let me install it!)

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

(I already have a user style manager, let me install it!)

// ==UserScript==
// @name        YouTube Wait for Me - Pause and Start Player in Background Tabs
// @author      Jefferson "jscher2000" Scher
// @namespace   JeffersonScher
// @version     0.7
// @copyright   Copyright 2016 Jefferson Scher
// @license     BSD 3-clause
// @description Pause the video in YouTube tabs opened in the background, play on activation 2016-08-18 (I know, it doesn't pause fast enough)
// @include     http*://www.youtube.com/*
// @grant       none
// ==/UserScript==
// See: https://developer.mozilla.org/docs/Web/API/Page_Visibility_API

var videoElement = document.querySelector('#movie_player video');
if (videoElement){
  if (document["hidden"]) { // background tab
    // Mute the player ASAP
    videoElement.muted = true;
    // Pause the player
    videoElement.pause();
    // Seek to the beginning
    videoElement.currentTime = 0;
    // Set up event handler to watch for tab becoming visible
    document.addEventListener("visibilitychange", handleVisibilityChange, false);
  }
}

function handleVisibilityChange() {
  if (document["hidden"]) {
    // Pause the player
    videoElement.pause();
  } else {
    // Resume the video after a quarter second
    window.setTimeout(function(){videoElement.play()}, 250);
    videoElement.muted = false;
    // We're not going to pause again, so remove event listener
    document.removeEventListener("visibilitychange", handleVisibilityChange, false);
  }
}