javascript:怎么在下页取得FORM表单的值

javascript:如何在下页取得FORM表单的值？
具体内容如下：
a.jsp
<form   type= "post "   action= "b.jsp ">
<input   name= "aa "   type= "hidden ">
</form>

b.jsp
<script   type= "text/javascript ">
  如何得到aa的值？
</script>

------解决方案--------------------
具体内容如下：
a.jsp
<form type= "post " action= "b.jsp ">
<input name= "aa " type= "hidden ">
</form>

b.jsp
<script type= "text/javascript ">
如何得到aa的值？
var a=Request( "aa ")
Response.Write( "a ")
</script>