<!DOCTYPE html>
<html>
<head>
<script src="/jquery/1.8/jquery.min.js"></script>
<meta charset=utf-8 />
<title>JS Bin</title>
<script>
$(document).ready(function(){
$("#txt").keyup(function(){
var v=$("#txt").val();
var reg=/^1?[1-9]?\d([.]\d)?$/;
var r=reg.test(v);
$("#re").text(r);
});
});
</script>
</head>
<body>
<input type="text" id="txt" >
<span id="re"></span>
</body>
</html>
