js获取封装对象/通过id tag className

<script language="javascript" type="text/javascript">
/*-------------封装开始------------------*/
function GetId(id){return document.getElementById(id)}  //通过ID获取对象
function GetTag(tag){return document.getElementsByTagName(tag)}  //通过Tag获取对象
function GetChildTag(id,tag){return id.getElementsByTagName(tag)}  //通过Tag获取ID的子对象
function GetClass(className){return getElementsByClassName(className)}  //通过className获取对象
var $c=function(array){var nArray = [];for (var i=0;i<array.length;i++) nArray.push(array[i]);return nArray;};
    Array.prototype.each=function(func){for(var i=0,l=this.length;i<l;i++) {func(this[i],i);};};
var getElementsByClassName=function(cn){
        var hasClass=function(w,Name){
        var hasClass = false;
        w.className.split(' ').each(function(s){
            if (s == Name) hasClass = true;
        });
        return hasClass;
            };
        var elems =document.getElementsByTagName("*")||document.all;
            var elemList = [];
           $c(elems).each(function(e){
               if(hasClass(e,cn)){elemList.push(e);}
           })
            return $c(elemList);
    };        
/*-----------------封装结束---------------------*/
window.onload=function(){
     GetTag("input")[0].onclick=function(){alert("id为test的div内容是：\n"+GetId("test").innerHTML)}
                 GetTag("input")[1].onclick=function(){alert("body里共有"+GetTag("li").length+"个li")}    
                 GetTag("input")[2].onclick=function(){alert("DIV里共有"+GetChildTag(GetId("test"),"li").length+"个li")}
                 GetTag("input")[3].onclick=function(){alert("className为test2的内容是：\n"+GetClass("test2")[0].innerHTML+"\n"+GetClass("test2")[1].innerHTML)}
    }
</script>

<div id="test" title="这是id=test的div">
    <ul title="div内第一个ul">
      <li>ccontent1</li>
      <li>ccontent2</li>
      <li>ccontent3</li>
      <li>ccontent4</li>
    </ul>
    <ul class="test2" title="div内第二个ul，class=test2">
       <li>bcontent1</li>
       <li>bcontent2</li>
       <li>bcontent3</li>
    </ul>
</div>
<ul class="test2" title="div外的ul，class=test2">
  <li>content1</li>
  <li>content2</li>
</ul>
<input type="button" value="通过id获取" />
<input type="button" value="通过tag获取" />
<input type="button" value="通过id内tag获取" />
<input type="button" value="通过className获取" />