Numeric validation on textbox using jQuery

<html>
<head>
<title>Number validation using jQuery with decimal and minus sign</title>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
</head>
<body>
<div>
<h3>Numeric validation on this textbox</h3>
<input type="text" class="txtnumval" /><br />
</div>
</body>
<script>
// JQUERY ".Class" SELECTOR.
$(document).ready(function() {
$('.txtnumval').keypress(function (event) {
return isNumber(event, this)
});
});
// THE SCRIPT THAT CHECKS IF THE KEY PRESSED IS A NUMERIC OR DECIMAL VALUE.
function isNumber(evt, element) {
var charCode = (evt.which) ? evt.which : event.keyCode
if (
(charCode != 45 || $(element).val().indexOf('-') != -1) && // “-” CHECK MINUS, AND ONLY ONE.
(charCode != 46 || $(element).val().indexOf('.') != -1) && // “.” CHECK DOT, AND ONLY ONE.
(charCode < 48 || charCode > 57))
return false;
return true;
}
</script>
</html>