js有关问题,为什么获取不了id元素?求解

2012-08-22

js问题,为什么获取不了id元素??求解PicList.prototype.run function(){ log(this.elem) //null } 这句获

js问题,为什么获取不了id元素??求解
PicList.prototype.run = function(){ log(this.elem) //null } 这句获取了空值...哪里出错了?

JScript code

function log(i){ return console.log(i); }     function $ (id)    {        if(typeof id === "string"){            return document.getElementById(id);        }else{            return id;        }    }    function PicList(){        this.elem = $(arguments[0]);        this.arr = [];        var iTarget = [            { left:0 },            { left:50 },            { left:100 },            { left:150 },            { left:200 }        ];                this.run();    }    PicList.prototype.run = function(){        log(this.elem)  //null    }    Animate.prototype = new PicList("wrap");    function Animate(){        log(this.arr)    }    var obj = new Animate();//HTML<div id="wrap">    </div>

[解决办法]
<script type="text/javascript">
function log(i){ return console.log(i); }

function $ (id)
{
if(typeof id === "string"){
return document.getElementById(id);
}else{
return id;
}
}
function PicList(){
this.elem = $(arguments[0]);
alert(this.elem.id);
this.arr = [];
var iTarget = [
{ left:0 },
{ left:50 },
{ left:100 },
{ left:150 },
{ left:200 }
];

this.run();
}
PicList.prototype.run = function(){
log(this.elem) //null
}
</script>

</head>

<body>
<div id="wrap"> </div>
<script type="text/javascript">
Animate.prototype = new PicList("wrap");
function Animate(){
log(this.arr)
}
var obj = new Animate();
</script>
这样试试貌似是因为Animate.prototype = new PicList("wrap");时你的那个div还没加载进来，所以为null
我也是猜的 js继承那块没好好看

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js有关问题,为什么获取不了id元素?求解