Validating Multiple Checkbox with example

< ? for(..)?>
  < input type="checkbox" name="couponlist[]" value="couponId;?>" >
< ? }?>

Validation Script:
function validateRemove() {
    var chk = document.getElementsByName('couponlist[]');
    var len = chk.length;
    var flag = 0;
    for (i = 0; i < len; i++) {   
        if(    chk[i].checked == true ){
            flag = 1;
        }
    }
    if(flag == 1) {
        if(confirm('Are you sure you want to remove selected coupons')){
            document.forms.couponlist.submit();
        }
    } else {
        alert('Select atleast one coupon to remove');
        return false;
    }
}