radiogroup的有关问题

radiogroup的问题
radiogroup的问题
我这样写
function   radiogroup(){

  var   fieldradiogroup   =   document.forms[0].radiogroup;
var   valueradiogroup   =   fieldradiogroup.value;
alert(valueradiogroup);

}

form里面的内容
是 <input   type= "radio "   name= "radiogroup "   value= "paystub "   onclick= "radiogroup() "   > 否 <input   type= "radio "   name= "radiogroup "   value= "messagequestion "   checked   onclick= "radiogroup() ">
为什么我选定之后会弹出报错对话框说不 "对象不支持此属性和方法 "哦??

[解决办法]
function radiogroup(){

var fieldradiogroup = document.getElementsByName( "radiogroup ");
for(i = 0;i <fieldradiogroup.length;i++)
{
alert(fieldradiogroup[i].value);
}
}