Javascript to accept only number for a form text field

I've developed a cross browser compatability script to accept only numbers for a text field on the web page. This works based on the browser events. IE supports the Javascript events in a way which is completely different from the other browsers like Firefox, Google Chrome, etc.

window.event - construct can be used to tackle the events on Internet Explorer.
event - pass the event while invoking the function, which can be used to deal with the events on non IE browsers like Firefox and Chrome.

<script type="text/javascript">
function onlyNumbers(evt)
{
    var e = (window.event)?event:evt; // for cross browser compatibility
    var charCode = e.which || e.keyCode;
    if (charCode > 31 && (charCode < 48 || charCode > 57)){
        return false;
    }
    return true;
}
</script>

Include the above script on your page and invoke the function onlyNumbers function onkeypress event of the corresponding text field with a return statement.

<input type="text" name="p_request" maxlength="10" onKeyPress="return onlyNumbers(event)">

Here is an example - try with the below text box

Text field