<html>
<head>
<script src="http://www.w3school.com.cn/jquery/jquery.js"></script>
<script>
$(function(){
$("#a").focus();
$("*").each(function(i){
alert($(this)[0].tagName);
})
})
</script>
</head>
<body>
<input id="a" type="text" value="aaa">
<input id="b" type="text" value="aaa">
</body>
</html>
