document.forms 获取 name 得到select 对象

 < html >
 < body >
 < form name = "t_form" >
     < select name = "t_select" >
     < option value = "first" selected > 1 <  / option >
     < option value = "second" > 2 <  / option >
     <  / select >
     <  / form >
     < script >
    var obj = document.forms['t_form'].t_select
    var index = obj.selectedIndex;
    alert(obj.options[index].value)
 <  / script >
 <  / body >
<  / html >