Question

I have an ‘object’:

function Rock()
{
    this.size = 30.0;
    this.body;
    this.isDead = false;

    this.vertexPosBuffer;
    this.vertexColBuffer;
}

which I give a function:

Rock.prototype.Tick = function()
{
    this.body.ApplyForce(new b2Vec2(0, 10), this.body.GetPosition());
}

and then I make an array of rocks:

var rocks;
function NewRandomRock()
{
    var newRock = new Rock;
    var pos = new b2Vec2;
        pos.x = Math.random()*(gl.viewportWidth+1);
        pos.y = Math.random()*(gl.viewportHeight+1);
    newRock.InitRand(pos);
    rocks.push(newRock);
}

and then I call the Tick function:

function TickRocks()
{
    for(var rock in rocks)
    {
        rock.Tick();
    }
}

Now the problem, I get the following error:

Uncaught TypeError: Object 0 has no method ‘Tick’

Though the “InitRand(…)” methods, which I add to the Rock the same way, does work…

What am I doing wrong ?

Answer 1

Your problem is that using for in is not made for iterating over arrays. It’s made to enumerate over object properties.

You should use a normal for loop:

for(var i = 0; i < rocks.length; i++) {
    rocks[i].Tick();
}