js 验证金额

<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>Untitled Page</title>
</head>
<body>
<input type="text" onchange="checknumber(this.value)" />
<input type="button" value="a" onclick="ab()" />

</body>

</html>
<script type="text/javascript">
function   checknumber(data){
var   tmp   ;
if   (data   ==   "")   return   true;
var   re   =   /^[\-\+]?([0-9]\d*|0|[1-9]\d{0,2}(,\d{3})*)(\.\d+)?$/;
return   re.test(data);
}
function ab()
{
     alert(checknumber("123.00"));