Allow only numeric value through Javascript

Below JavaScript will allow only to enter numeric value in Textbox. This javascript can be used for Mobile number, Salary, Budget, etc.

Include below JavaScript
<script language="javascript" type="text/javascript">
function isNumber(field)
{
    var textbox = document.getElementById(field);
    var re = /^[0-9]*$/;
    if (!re.test(textbox.value))
    {
        textbox.value = textbox.value.replace(/[^0-9]/g,"");
    }
}
</script>

Call this fuction in HTML as given below:
<input type="text" name="test" id="test" onkeyup="isNumber('test');" />