Why is my simple JavaScript numbers, and delete only, checker not working?

Question

I have a very simple piece of JavaScript that is not working 100%, and I can't figure out why.

<input type="text" onKeyPress="return numbersOnly(event);" />

function numbersOnly(event){
    // Return "true" for all numbers and the delete (a.k.a., backspace) key.
    return ((event.charCode >= 48 && event.charCode <= 57) || event.charCode == 8) ? true : false;
}

It will let me input just the numbers exactly like I want, but it won't pick up the delete (a.k.a., backspace) key.

EDIT: The weird thing is this works for me in IE 9 but not Firefox.

Related: [“keypress” doesn't detect backspace?](http://stackoverflow.com/questions/4843472/javascript-listener-keypress-doesnt-detect-backspace) — Jonathan Lonowski, Oct 21 '14 at 15:58
@JonathanLonowski I changed it to "keydown" but now nothing works. — Brian, Oct 21 '14 at 16:07

score 2 · Accepted Answer · answered Oct 21 '14 at 16:23

You're facing some cross browser issues with events. Try this

function numbersOnly(event) {
    var key = (event.hasOwnProperty('charCode')) ? event.charCode : event.which;
    // Return "true" for all numbers and the delete (a.k.a., backspace) key.
    return ((key >= 48 && key <= 57) || key == 8) ? true : false;
}

Why is my simple JavaScript numbers, and delete only, checker not working?

1 Answers1