<div id="id1" style="width:200px; height:200px; position:absolute; top:100px; left:100px; background-color:blue; z-index:4"><div id="id2" style="width:200px; height:200px; position:absolute; top:20px; left:70px; background-color:green; z-index:1"></div> </div>
addEventListener中的第三个参 数是useCapture, 一个bool类型。当为false时为冒泡获取(由里向外)，true为capture方式(由外向里)。
eg1：
document.getElementById(‘id1’).addEventListener(‘click’, function() { console.log(‘id1’);}, false);document.getElementById(‘id2’).addEventListener(‘click’, function() { console.log(‘id2’);}, false);点击id2的div结果是: id2， id1document.getElementById(‘id1’).addEventListener(‘click’, function() { console.log(‘id1’);}, false);document.getElementById(‘id2’).addEventListener(‘click’, function() { console.log(‘id2’);}, true);结果是: id2, id1document.getElementById(‘id1’).addEventListener(‘click’, function() { console.log(‘id1’);}, true);document.getElementById(‘id2’).addEventListener(‘click’, function() { console.log(‘id2’);}, false);结果是：id1，id2document.getElementById(‘id1’).addEventListener(‘click’, function() { console.log(‘id1’);}, true);document.getElementById(‘id2’).addEventListener(‘click’, function() { console.log(‘id2’);}, true);结果是：id1，id2
，偶尔会想，如果人生真如一场电子游戏，
