Strange onkeypress event with ESC in Firefox...

**sekter** · 05-14-2010 04:06 AM

Hi all,
I have the following code:

<input onkeydown="return testKey(event)" type="text"/>
function testKey(evt)
{
var charCode = (evt.which) ? evt.which : event.keyCode;
alert(charCode)
}

- This code works perfectly in IE with no errors
- In Firefox (Using FireBug to check for JS errors) the code alerts every character fine except for 1 key which is the ESC key. When i press the ESC key in that input field FireBug throws an error saying: "event is not defined". So for some retarded reason Firefox is looking at the event.keyCode part (which is supposed to be used for IE only) for only the ESC key (all other keys dont throw up an error).

EDIT: Ok i have figured out why its happening now, because Firefox charCode returns 0 and IE returns undefined and when you do 0 || undefined it returns undefined which i didnt think would be the case. Anyone have an idea how to get around the ESC key besides detecting for 0 and undefined?

**Fang** · 05-14-2010 06:00 AM

Code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">

<script type="text/javascript">
window.onload=function() {
document.getElementsByTagName('input')[0].onkeydown = testKey;
};

function testKey(e) {
var evt = window.event? window.event : e;
var keyCode = window.event? evt.keyCode : (evt.charCode || evt.which);
if(keyCode == 27) {return false;}
}
</script>

<style type="text/css">
* {margin:0;padding:0;}
</style>

</head>
<body>
<form action="#" name="form1">
<div>
<input type="text" name="field">
</div>
</form>
</body>
</html>

**sekter** · 05-14-2010 06:16 AM

Hi Fang,
Thank you for that, however if i needed to allow say for example only letters to be input in a field (including things like backspace, left arrow, right arrow, space) am i right in saying that this is the best way to do it?
var evt = window.event? window.event : e;
var keyCode = window.event? evt.keyCode : (evt.charCode || evt.which);
alert(keyCode)

if ( (keyCode > 64 && keyCode < 91) ||(keyCode > 96 && keyCode < 123) )
{
return true;
}

if(keyCode==0)
{
//check charCode value to see if the key pressed was a left, right arrow or backspace. If it was any of those 3 then also return true
}

EDIT: The problem im having is that if i detect certain keys to allow them (like letters only in the above example) then i need to also account for left and right arrow keys which have a keycode value of 0...

Do you rekon IE would be happy with this?

**Fang** · 05-14-2010 06:36 AM

Then allow "8,32,37,and 39" Backspace, space, left-arrow and right-arrow

**sekter** · 05-14-2010 06:40 AM

I did that before however i ran into a problem, using your code if you allow the 37 keycode (for left arrow) then you are also allowing the "%" character aswell because it has a charCode of 37 and keycode of 0.

**Fang** · 05-14-2010 06:48 AM

No, detect the shiftKey

Code:

if(e.shiftKey && keyCode == 53) {alert('&#37;');}

**sekter** · 05-14-2010 06:53 AM

Ah right your using onkeydown whereas im using onkeypress that explains it, is it preferable to use the onkeydown instead? (Im just getting mixed up as to which one should be used where).

**Fang** · 05-14-2010 06:59 AM

onkeydown gives more consistent results across browsers.

**sekter** · 05-14-2010 07:06 AM

Thanks alot Fang i will start using onkeydown from now on.

**Kor** · 05-14-2010 08:05 AM

See also the differences and the lack of consistency regarding the key capturing in different browsers:

http://www.quirksmode.org/js/keys.html

**sekter** · 05-14-2010 08:36 AM

Thanks Kor, i was actually using this website alot to test for certain keys but when i read the special keys section i didnt realise other keys like arrow keys would also cause problems too.
Cheers for pointing that out aswell, appreciated

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