checkbox 的问题高手帮忙看看
<script>

function chk(obj1){

var obj = document.getElementsByName(obj1);
var j = 0;
if (obj.length){
for (i = 0; i < obj.length; i++){
if (obj[i].checked) j++;
if (j > 3){
alert( "对不起，最大选取3。 ");
obj1.checked = false ;

break;

}
}
}
}
</script>

<INPUT type= "checkbox " name= "uid1 " value= "1 " onClick= "chk(this.name); ">
<INPUT type= "checkbox " name= "uid1 " value= "2 " onClick= "chk(this.name); ">
<INPUT type= "checkbox " name= "uid1 " value= "3 " onClick= "chk(this.name); ">
<INPUT type= "checkbox " name= "uid1 " value= "4 " onClick= "chk(this.name); "> <INPUT type= "checkbox " name= "uid1 " value= "5 " onClick= "chk(this.name); ">
选择超过3个提示信息点确定后，勾选为何不去掉，高手看看问题出在哪里


------解决方案--------------------
<script>

function chk(obj1){

var obj = document.getElementsByName(obj1.name);
var j = 0;

for (i = 0; i < obj.length; i++){
if (obj[i].checked) j++;
if (j > 3){
alert( "对不起，最大选取3。 ");
obj1.checked = false ;

break;

}
}
}
</script>

<INPUT type= "checkbox " name= "uid1 " value= "1 " onClick= "chk(this); ">
<INPUT type= "checkbox " name= "uid1 " value= "2 " onClick= "chk(this); ">
<INPUT type= "checkbox " name= "uid1 " value= "3 " onClick= "chk(this); ">
<INPUT type= "checkbox " name= "uid1 " value= "4 " onClick= "chk(this); ">
<INPUT type= "checkbox " name= "uid1 " value= "5 " onClick= "chk(this); ">