事件委托示例

代码

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button id="add">添加</button>
    <ul id="list">
        <li>11</li>
        <li>22</li>
        <li>33</li>
    </ul>

    <script>
        var lis = document.getElementsByTagName('li');
        var add = document.getElementById('add');
        // for(var i=0;i<lis.length;i++){  // 0 1 2
        //     lis[i].index = i;
        //     lis[i].onclick = function(){
        //         alert(this.index);
        //     }
        // }
       

        add.onclick = function(){
            var newLi = document.createElement('li');
            newLi.innerHTML = 'ccc';
            list.appendChild(newLi);
        }

        list.onclick = function(ev){   // 将事件委托给父元素 ul，由ul来分配给子元素
            var eve = event || ev;
            console.log(eve.target);
            eve.target.style.background = 'pink';
        }
    </script>
</body>
</html>
效果

事件委托示例