为什么dom2不能调用do()函数？调用show（）却可以
<!DOCTYPE html>
<html>
<head>
<title>DOM2事件处理程序</title>
<meta charset="utf-8">
</head>
<body>
<input id="html" type="button" value="按钮1" onclick="show()">
<input id="dom0" type="button" value="按钮2" >
<input id="dom2" type="button" value="按钮3">
<script type="text/javascript">
function show(){
alert("HTML事件处理程序");
}
function do(){
alert("DOM2事件处理程序");}
var dom0=document.getElementById("dom0");
dom0.onclick=function(){
alert("DOM0级事件处理程序");}
/*dom0.onmousemove=function(){
alert("哈哈");
}*/
//dom0.onclick="null";
var dom2=document.getElementById("dom2");
dom2.addEventListener("click",do
,false);
dom2.addEventListener("click",function(){
alert("二次哈哈");
},true);
</script>
</body>
</html>
