事件委托

1. 不用給子元素循環(huán)綁定事件，提高性能
2. 新添加的子元素，仍能保留原有事件

Event 對(duì)象兼容處理

IE ：window.event.srcElement
標(biāo)準(zhǔn)：event.target
兼容寫法

function(e){
    var e = e || window.event;
    var target = ev.target || e.srcElement;
    alert(target.innerHTML);// 對(duì)目標(biāo)元素處理，檢測(cè)
}

下面貼一段代碼演示

<ul id="ul">
    <li>11</li>
    <li>22</li>
    <li>33</li>
</ul>

var oUl = document.getElementById('ul1');
var aLi = oUl.getElementsByTagName('li');

oUl.onmouseover = function(ev){
    var ev = ev || window.event;
    var target = ev.target || ev.srcElement;
    // 用nodeName節(jié)點(diǎn)名判斷是子元素還是父元素
    if(target.nodeName.toLowerCase() == 'li'){
        target.style.background = 'red';
    }
};
oUl.onmouseout = function(ev){
    var ev = ev || window.event;
    var target = ev.target || ev.srcElement;

    if(target.nodeName.toLowerCase() == 'li'){
        target.style.background = '';
    }
};