1.html代码如下：
<html> <head> </head> <body> <form name="form1" id="form1"> Select your favorite fruit: <select id="mySelect" name="mySelect"> <option value="11">Apple</option> <option value="22" >Orange</option> <option value="33">Pineapple</option> <option value="44">Banana</option> </select> <br /><br /> <input type="button" onclick="getIndex()" value="Alert index of selected option"> </form> </body> </html>
2.javascript代码如下：
<script type="text/javascript">
function getIndex()
{
//从document对象中，获取select标签
var a=document.getElementById("mySelect");
//select标签获取的值其实是一个数组--a.options[]; 然后，选定项的下标是--a.selectedIndex
var b=a.options[a.selectedIndex].value;
alert(b);
}
</script>