如何减少javascript事件对内存性能的影响
我们知道浏览器使用的是os的内存，而且是受限制的，远小于os内存，
如果在页面里添加了过多的事件，那么由于事件处理函数过多，会造成内存占用过大，严重影响性能，同时过多的事件会降低页面的交互性。
那么如何有效减少事件处理函数的个数呢？

< ul id=”myLinks” >< li id=”goSomewhere” > Go somewhere < /li >< li id=”doSomething” > Do something < /li >< li id=”sayHi” > Say hi < /li >< /ul >

//优化前

var item1 = document.getElementById(“goSomewhere”);var item2 = document.getElementById(“doSomething”);var item3 = document.getElementById(“sayHi”);EventUtil.addHandler(item1, “click”, function(event){location.href = “http://www.wrox.com”;});EventUtil.addHandler(item2, “click”, function(event){document.title = “I changed the document ’ s title”;});EventUtil.addHandler(item3, “click”, function(event){alert(“hi”);});

//优化后

var list = document.getElementById(“myLinks”);EventUtil.addHandler(list, “click”, function(event){event = EventUtil.getEvent(event);var target = EventUtil.getTarget(event);switch(target.id){case “doSomething”:document.title = “I changed the document ’ s title”;break;case “goSomewhere”:location.href = “http://www.wrox.com”;break;case “sayHi”:alert(“hi”);break;}});

2.及时移除事件，释放内存
先看一个反例：

< div id=”myDiv” >< input type=”button” value=”Click Me” id=”myBtn” >< /div >< script type=”text/javascript” >var btn = document.getElementById(“myBtn”);btn.onclick = function(){//do somethingdocument.getElementById(“myDiv”).innerHTML = “Processing...”; //Bad!!!};< /script >

正解：

< div id=”myDiv” >< input type=”button” value=”Click Me” id=”myBtn” >< /div >< script type=”text/javascript” >var btn = document.getElementById(“myBtn”);btn.onclick = function(){//do somethingbtn.onclick = null; //remove event handlerdocument.getElementById(“myDiv”).innerHTML = “Processing...”;};< /script >