Twitch Auto Pause/Play Toggle for Tab Switch

Attempts to Save Resources by Auto Pausing/Playing Different Open Twitch Streams
当前为 2019-09-08 提交的版本，查看最新版本。
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// ==UserScript==
// @name          Twitch Auto Pause/Play Toggle for Tab Switch
// @namespace     http://userstyles.org
// @description   Attempts to Save Resources by Auto Pausing/Playing Different Open Twitch Streams
// @author        636597
// @include       *://*.twitch.tv/*
// @run-at        document-start
// @version       0.3
// ==/UserScript==


var PLAYING = true;
var PAUSE_PLAY_BUTTON_ELEMENT = false;
var CHECKING_FOCUS = true;
var button_element = false;

function toggleCheckFocus() {
	if ( CHECKING_FOCUS ) {
		console.log( "Stopping Observing the Focus" );
		clearObserver();
		button_element.innerHTML = 'Observe Focus';
	}
	else {
		console.log( "Starting Observing the Focus" );
		loadObserver();
		button_element.innerHTML = 'Stop Observing Focus';
	}
	CHECKING_FOCUS = !CHECKING_FOCUS;
}
function addToggleCheckFocusButton() {
	//var title_element = document.querySelector( 'h2[data-a-target="stream-title"]' );
	var title_element = document.querySelector( 'div[data-test-selector="chat-input-buttons-container"' )
	//if ( !title_element ) { return; }
	var id = "toggle-check-focus";
	var element_string = '<button id="' + id + '">Stop Observing Focus</button>';
	var template = document.createElement( 'template' );
	template.innerHTML = element_string;
	var fragment = template.content
	title_element.insertBefore( fragment ,  title_element.childNodes[ title_element.childNodes.length - 1 ] );
	button_element = document.body.querySelector( "#" + id );
	button_element.addEventListener( "click" , function( event ) {
		toggleCheckFocus();
	});
}

function checkFocus() {
	if ( document.hasFocus() ) {
		// console.log( "tab enter" );
		// console.log( "PLAYING === " + PLAYING );
		if ( !PLAYING ) {
			console.log( "Tab Entered: Toggling Play State" );
			PAUSE_PLAY_BUTTON_ELEMENT.click();
			PLAYING = true;
		}
	} else {
		// console.log( "tab leave" );
		// console.log( "PLAYING === " + PLAYING );
		if ( PLAYING ) {
			console.log( "Tab Left: Toggling Play State" );
			PAUSE_PLAY_BUTTON_ELEMENT.click();
			PLAYING = false;
		}
	}
}

// Maybe It Be Converted to Observer Somehow
var observer_interval = false;
function clearObserver() {
	clearInterval( observer_interval );
}
function loadObserver() {
	console.log( PAUSE_PLAY_BUTTON_ELEMENT );
	if ( !PAUSE_PLAY_BUTTON_ELEMENT ) { return; }
	observer_interval = setInterval( checkFocus, 1000 );
}

// Init
(function() {
	var ready = setInterval(function(){
		var x1 = document.querySelectorAll( 'button.player-button' );
		if ( x1 ) { if ( x1[ 0 ] ) {
			PAUSE_PLAY_BUTTON_ELEMENT = x1[0];
			clearInterval( ready );
			addToggleCheckFocusButton();
			loadObserver();
		}}
	} , 2 );
	setTimeout( function() {
		clearInterval( ready );
	} , 10000 );
})();