Javascript Error While Dropping Balls

I wrote a javascript code to drop in ball multiple times when clicked on canvas. It is an experiment. Here is the code: HTML

for (var i = 0; i < balls.length; i++)

or if you do not want to change the loop, you can initialize 3 balls at the start:

balls = [ball1, ball2, ball3];

where ball1, ball2 and ball3 are defined as how your ball data type is.

EDIT:

As I understand, you have some number of contexts, and for each context, you want to have a list of balls so that you can draw them.

Then:

balls = []

for (var i = 0; i < canvases.length; i++) {
    context.push(canvases[i].getContext('2d'));
    balls.push([]);
}

and use the remaining code same.