Question

I Have this JavaScript code to allow only numeric input on textboxes

    function CheckNumeric(e) {

        if (window.event) // IE 
        {
            if ((e.keyCode < 48 || e.keyCode > 57) & e.keyCode != 8) {
                event.returnValue = false;
                return false;
            }
        }
        else { // Fire Fox
            if ((e.which < 48 || e.which > 57) & e.which != 8) {
                e.preventDefault();
                return false;
            }
        }
    }

The problem is that it’s also preventing the "TAB" button! which I like to allow.

How can I do that?

Answer 1

I would change the CheckNumeric function into something like this and use a regex to determine valid/invalid input. /[0-9\t\b]+/ matches numbers, tabs and backspace. if you also want to allow space change it to /[0-9\t\b\s]+/

function CheckNumeric(e)
{
    var charCode = e.charCode || e.keyCode;
    var character = String.fromCharCode(charCode);
    if(!character.match(/[0-9\t\b]+/))
    {
        if(window.event)
            event.returnValue = false;
        else
            e.preventDefault();
        return false;
    }
    return true;
}

additionally, in order to capture keycodes correctly you should bind to the onKeyPress event instead of onKeyDown as it will not provide correct keycodes for the numeric keypad.

<input type="text" onkeypress="CheckNumeric(event)"/>