JavaScript KeyDown event not triggered when multiple keys are held down

Question

I am experiencing a strange problem with JavaScript. I am working on a HTML5 canvas game that uses keyboard input. The two player mode of the game involves up to 6 keys on the keyboard being pressed and held down.

It seems like the "keyDown" event stops being called after I hold 4 or 5 keys down on the keyboard.

The code I am using is below:

window.onkeydown = function (event) { console.log(event.keyCode); input.onKeyDown(event.keyCode); };

The console should log a key code for each key I press down. However, it only seems to report the keycode for the first 4 or 5 I hold down. This is causing the controls for the two player version of my game to not work when both players press too many keys.

Is this a bug, a limitation of JavaScript/HTML5, or am I doing something wrong?

possible duplicate of javascript multiple keys pressed at once — putvande
– putvande, Commented Aug 9, 2013 at 20:55
I believe the problem is not so much a JavaScript problem as it is a hardware problem. w3schools.invisionzone.com/index.php?showtopic=45663 — Steven Lambert
– Steven Lambert, Commented Aug 9, 2013 at 21:47
I found out that, if you keep down 3 arrow keys, if you press a fourth one, it is ignored. Indeed suspicious. — Ambroise Rabier
– Ambroise Rabier, Commented Jan 26, 2020 at 19:13

jknight · Accepted Answer · 2013-11-16 19:05:00Z

2

This is a limitation of the USB keyboard not of your code!

answered Nov 16, 2013 at 19:05

jknight

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