<!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>
<title>Untitled Page</title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3/jquery.min.js"></script>
<script type="text/javascript" language="javascript">
$(function(){
//Bind the change event
$("#dropLang").unbind("change", eDropLangChange).bind("change", eDropLangChange);
$("#dropFrame").unbind("change", eDropFrameChange).bind("change", eDropFrameChange);
});
//The change event of language dropdown-list
var eDropLangChange = function(){
//The selected value of the language dropdown-list.
var selectedValue = $(this).val();
//show all options.
$("#dropFrame").children("span").each(function(){
$(this).children().clone().replaceAll($(this)); //use the content of the <span> replace the <span>
});
//Filter the data through selected value of language dropdown-list except <Please Select>.
//If the option is <Please Select>, it only needs to show all and hide nothing.
if(parseInt(selectedValue) != 0){
//hide the option whose parentid is not equal with selected value of language dropdown-list.
//The <Please Select> option should not be hidden.
$("#dropFrame").children("option[parentid!='" + selectedValue + "'][value!='0']").each(function(){
$(this).wrap("<span style='display:none'></span>"); //add a <span> around the <option> and hide the <span>.
});
}
};
//The change event of frame dropdown-list.
var eDropFrameChange = function(){
//Find the selected option of frame dropdown-list. set the value of language dropdown-list by selected parentid.
$("#dropLang").val($(this).children("option:selected").attr("parentid"));
};
</script>
</head>
<body>
<div>
<select id="dropLang">
<option selected="selected" value="0"><Please Select></option>
<option value="1">Javascript</option>
<option value="2">Java</option>
<option value="3">C#</option>
</select>
<select id="dropFrame">
<option selected="selected" value="0"><Please Select></option>
<option value="1" parentid="1">JQuery</option>
<option value="2" parentid="1">Prototype</option>
<option value="3" parentid="2">Struts</option>
<option value="4" parentid="2">Spring</option>
<option value="5" parentid="2">Velocity</option>
<option value="6" parentid="2">Hibernate</option>
<option value="7" parentid="3">ASP.NET MVC</option>
<option value="8" parentid="3">Castle</option>
</select>
</div>
</body>
</html>