Question

I have a function like this:

function foo(canvas) {
    canvas.mousedown(function(e) {
        console.log(canvas); //undefined
    });
}

I’m calling foo on mouse click in a certain spot of the page.

Why is canvas undefined?

Answer 1

The problem was this:

function foo(canvas) {
    canvas.mousedown(function(e) {
        console.log(canvas); //undefined
        //...
        for (var i in array) {
            var canvas = array[i].canvas;
            //...
        }
    });
}

I haven’t time to investigate the exact reason. My guess is that the compiler puts a “var canvas” declaration at the start of the anonymous function, such that the variable is undefined when output in the console. Otherwise don’t understand it yet.