checkbox二选一

 <script type="text/javascript">
 var flag = true;
 function check(){
var check1=document.getElementById("next1");
var check2=document.getElementById("next2");
if(check1.checked&&flag){
check2.checked=false;
flag = false;

}
if(check2.checked&&!flag){
check1.checked=false;
flag = true;

}
}


 </script>