How can convert this code by using forms not prompt !

Question

<?xml version="1.0" encoding="utf-8" ?>
Assignment 2

var count;
// the number of value that you want to check if number or no
count=window.prompt("please enter value for count ");
var c;
c=parseInt(count);
if(!isNaN(c))
window.alert("The Value Is Number ! ");
else
{
window.alert("SorrY . The Value is Not Number (NaN ) ");
c=window.prompt(" NOT NUMBER ! \n please enter value for count ");
}
while(c<0)
{
c=window.prompt(" NEGATIVE NUMBER ! \n please enter value for count ");
if(!isNaN(c))
window.alert("The Value Is Number ! ");
else
{
window.alert("SorrY . The Value is Not Number (NaN ) ");
c=window.prompt(" NOT NUMBER ! \n please enter value for count ");
window.alert(" POSITIVE NUMBER ");
}}
document.writeln("GooD . The Value is Positive ");