Limiting number value in an input tag with javascript

Question

I am creating a form and i want the input tag to accept numbers only and i also want to limit the numbers to be from 0 - 20.

This my html code:

<input type="text" name="three" class="actual" id="three" maxlength="2" onkeypress="return ForNumbers(event)" />

This is my javascript code:

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

Answer 1

If you need to support old browsers, try this:

    function ForNumbers(evt){
        var charCode = (evt.which) ? evt.which : event.keyCode;

        if (
        //0~9
        charCode >= 48 && charCode <= 57 ||
           //number pad 0~9
           charCode >= 96 && charCode <= 105 ||
        //backspace
           charCode == 8 ||
        //tab
        charCode == 9 ||
        //enter
        charCode == 13 || 
        //left, right, delete..
        charCode >= 35 && charCode <= 46
        )
        {
        //make sure the new value below 20
        if(parseInt(this.value+String.fromCharCode(charCode), 10) <= 20) 
            return true;
        }

        evt.preventDefault();
        evt.stopPropagation();

        return false;
    }

http://jsfiddle.net/3StSM/2/

It also works fine with:

  <input id="numIpt" type="number" min="0" max="20" maxlength="2" />