یک مثال ساده
[HTML]<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<script language="javascript" type="text/javascript">
function takhfif()
{
var g=document.getElementById('ghaymat').value;
var d=document.getElementById('dadsad').value;
var d=d.replace('%','');
var gwt=document.getElementById('gwt');
gwt.value=g-g*(d/100);
}
</script>
</head>
<body>
<input type="text" value="10000" id='ghaymat'/>
<label>قیمت</label>
<br />
<input type="text" id='dadsad' value="10%"/>
<label>تخفیف</label>
<br />
<input type="text" id='gwt' />
<label>قیمت با تخفیف</label>
<br />
<input type="button" value="محاسبه" onclick=" takhfif()"/>
</body>
</html>
[/HTML]