js正則驗證是否是數字（包括正整數,０,負整數,小數)

<script language="JavaScript" type="text/javascript">
function checkNum(obj)
{
 var re = /^-?[1-9]*(\.\d*)?$|^-?0(\.\d*)?$/;
     if (!re.test(obj.value))
    {
        alert("非法數字");
        obj.value="";
        obj.focus();
        return false;
     }
}
</script>

<input name="rate" type="text"onkeyup="checkNum(this)" />