js方法：

復制代碼 代碼如下:

<script type="text/javascript">

window.onload=function(){

var userName="xiaoming";

alert(userName);
}

</script>

復制代碼 代碼如下:

<script type="text/javascript">

$(document).ready(function(){

var userName="xiaoming";

alert(userName);
});

</script>

復制代碼 代碼如下:

$(function(){
var userName="xiaoming";
alert(userName);
});