My code works on Chrome but not on Firefox... in Firefox... whenever this piece of code launches..

canvas.addEventListener('keydown');

I get this error:

Not enough arguments
[Break On This Error]   

canvas.addEventListener('keydown');

I have var canvas near the top as well as this:

canvas = document.getElementById("canvas");
    canvas.width = 512;
    canvas.height = 352;
context = canvas.getContext("2d");

I do not know why it works fine on Chrome but not Firefox...

My code works on Chrome but not on Firefox... in Firefox... whenever this piece of code launches..

canvas.addEventListener('keydown');

I get this error:

Not enough arguments
[Break On This Error]   

canvas.addEventListener('keydown');

I have var canvas near the top as well as this:

canvas = document.getElementById("canvas");
    canvas.width = 512;
    canvas.height = 352;
context = canvas.getContext("2d");

I do not know why it works fine on Chrome but not Firefox...

• javascript
• html

• 6 The second argument to addEventListener should be the callback function. See: developer.mozilla.org/en-US/docs/DOM/element.addEventListener – asawyer Commented Aug 10, 2012 at 19:00
• 2 Of course that is javascript. The JQuery echivalent is .on – Samson Commented Aug 10, 2012 at 19:01

3 Answers 3

The addEventListener function needs a second parameter to specify the function that is called on the event. The real question is why Chrome doesn't generate an error.

You need a function that executes when the event fires. It can be specified either inline like this:

canvas.addEventListener('keydown', function(e) {
    // your code here to handle the event
});

or it can be specified like this:

function keyHandler(e) {
    // your code here to handle the event
}

canvas.addEventListener('keydown', keyHandler);

Without an event handler function, there is nothing for the event handler to do as no code would execute when the event fires.

You could also use JQuery to bind the keydown event to the canvas.

$('#canvas').on("keydown", function(event){
    // code
});