Hi Friend,

Try the following code:

<script type="text/javascript">
function check(){
            var num=document.getElementById('num').value;
            var i=2;
            var b;
            var status = true;
        while(i<num)
            {
                b=num%i;
                if(b==0)
                {
                    status = false;
                    break;
                }
                i++;
            }


            if (status)
            {
                alert("Your number is a prime number");
            }
            else
            {
                alert("Your number is not a prime number");
            }
            }
    </script>
    Enter Number to Check:<input type="text" id="num"><input type="button" value="Check" onclick="check();">

Thanks