【js小方法】提交表单是，判断单选框是否被选中

<p>单选，至少选择一个</p>
<form name="form1" method="post"  action="" onsubmit="return postform(this)">
<input type="radio" name="choose" id="input1" value="choose1">1
<input type="radio" name="choose" id="input1" value="choose2">2
<input type="submit" name="Submit" value=" 提交 ">
</form>

function postform(obj){
var obj2=document.getElementsByName("choose");
for(var i=0;i<obj2.length;i++){
if(obj2[i].checked==true){
temp=1;
break;
}else{
temp=0;
}
}
if(temp==0){alert("请选择");return false;}
}