求教，點擊按鈕后為什么沒有彈出對話框？有什么問題？
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>無標題文檔</title>
<script>
function message(){
alert("hello!");
}
var btn=document.getElementById("btn");
var eventUtil={
add:function(element,type,handler){
if(element.addEventListener){
element.addEventListener(type,handler,false);
}
else if(element.attachEvent){
element.attachEvent("on"+type,handler);
}
else{
element["on"+type]=handler;
}
}
}
eventUtil.add(btn,"click",message);
</script>
</head>
<body>
<input type="button" value="button" id="btn" />
</body>
</html>
2014-10-11
你好，var btn=document.getElementById("btn");這句執行的時候，文檔還未加載，你可以將js腳本放在<body>最后面，或者放在window.onload中
2014-10-10
<script>
function message(){
alert("hello!");
}
var eventUtil={
add:function(element,type,handler){
if(element.addEventListener){
element.addEventListener(type,handler,false);
}
else if(element.attachEvent){
element.attachEvent("on"+type,handler);
}
else{
element["on"+type]=handler;
}
}
}
window.onload=function(){
var btn=document.getElementById("btn");
eventUtil.add(btn,"click",message);
}
</script>