Og det er ganske rigtigt javascript, f.eks.
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"
http://www.w3.org/TR/html4/loose.dtd"><html>
<head>
<title>Tomt dokument</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style type="text/css">
html,body{height:100%;margin:0px;border:0px;padding:0px;font-family:tahoma,verdana,arial,sans-serif;font-size:small;}
</style>
<script language="javascript" type="text/javascript">
function updateSum(f){
var sum = chNumber(f.Pris1.value) + chNumber(f.Pris2.value) + chNumber(f.Pris3.value) + chNumber(f.Pris4.value) + chNumber(f.Pris5.value);
var rest = chNumber(f.PrisIalt.value) - sum;
document.getElementById('restSpan').innerHTML = rest;
f.Send.disabled = rest != 0;
}
function chNumber(tal){
if(!(""+tal).match(/^\d+(\.\d{0,2})?$/))
return 0;
else return + tal;
}
</script>
</head>
<body>
<form id="minForm" name="minForm">
Samlet pris: <input id="PrisIalt" name="PrisIalt" type="text" value="0" onfocus="if(this.value==this.defaultValue)this.value='';" onblur="if(this.value=='')this.value=this.defaultValue;" size="20" onchange="updateSum(this.form);"><br>
Pris 1: <input id="Pris1" name="Pris1" type="text" value="0" onfocus="if(this.value==this.defaultValue)this.value='';" onblur="if(this.value=='')this.value=this.defaultValue;" size="20" onchange="updateSum(this.form);"><br>
Pris 2: <input id="Pris2" name="Pris2" type="text" value="0" onfocus="if(this.value==this.defaultValue)this.value='';" onblur="if(this.value=='')this.value=this.defaultValue;" size="20" onchange="updateSum(this.form);"><br>
Pris 3: <input id="Pris3" name="Pris3" type="text" value="0" onfocus="if(this.value==this.defaultValue)this.value='';" onblur="if(this.value=='')this.value=this.defaultValue;" size="20" onchange="updateSum(this.form);"><br>
Pris 4: <input id="Pris4" name="Pris4" type="text" value="0" onfocus="if(this.value==this.defaultValue)this.value='';" onblur="if(this.value=='')this.value=this.defaultValue;" size="20" onchange="updateSum(this.form);"><br>
Pris 5: <input id="Pris5" name="Pris5" type="text" value="0" onfocus="if(this.value==this.defaultValue)this.value='';" onblur="if(this.value=='')this.value=this.defaultValue;" size="20" onchange="updateSum(this.form);"><br>
<input name="Send" type="submit" disabled>
</form>
Rest: <span id="restSpan">0</span>
</body>
</html>
