Q:

need to select atleast one checkbox using javascript

I am using this javascript code. and on button click I want that atleast one checkbox selection is required. do anyone have idea what I am doing wrong. I don't want to use jquery. 
    
function check()
{
var flag = false;
for(var i=1;i<=4;i++)
{
  var checkb = document.getElementById("check"+i);

  if(checkb.checked)
  {
    flag = true;
    break;
  }
}
if(!flag)
alert("What is your interest \n(select at least one option)");
return flag;
}
</script>

Button Click Code is 
<input type="submit" name="submit" value="Submit" onclick="return check();">

A:

The code works fine. Do hou have id="check1" set on your checkbox tags?

