firfox版：
<HTML>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<HEAD>
<TITLE></TITLE>
<script>
document.onclick=function(e){
var evt=e||window.event;
var tar=evt.target||evt.srcElement;
if( (tar.tagName.toLowerCase()=="input"&&tar.type=="button") || tar.tagName.toLowerCase()=="button"){
alert("你点击的是一个按钮")
}
}
</script>
</HEAD>
<BODY>
<input id="button1" type="button" value="1111"/>
<input id="button2" type="button" value="2222"/>
<input id="button3" type="button" value="3333"/>
<input id="button4" type="button" value="4444"/>
</BODY>
</HTML>
google 浏览器版：
<HTML>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<HEAD>
<TITLE></TITLE>
<script>
document.onclick=function()
{ var obj = event.srcElement;
if(obj.type == "button"){
alert(obj.id); }
}
</script>
</HEAD>
<BODY>
<input id="button1" type="button" value="1111"/>
<input id="button2" type="button" value="2222"/>
<input id="button3" type="button" value="3333"/>
<input id="button4" type="button" value="4444"/>
</BODY>
</HTML>