Unable to locate the JavaScript function

Question

Unable to locate the JavaScript function

My latest 'object' creation:

function Gem()
{
    this.size = 20.0;
    this.body;
    this.isCollected = false;

    this.vertexPosBuffer;
    this.vertexColBuffer;
}

Next, I define a function for it:

Gem.prototype.Update = function()
{
    this.body.ApplyForce(new b2Vec2(0, 5), this.body.GetPosition());
}

Finally, I populate an array with gems:

var gems;
function AddNewGem()
{
    var newGem = new Gem;
    var position = new b2Vec2;
        position.x = Math.random()*(canvas.width+1);
        position.y = Math.random()*(canvas.height+1);
    newGem.InitializeRandom(position);
    gems.push(newGem);
}

To update all gems, I use the following function:

function UpdateGems()
{
    for(var gem in gems)
    {
        gem.Update();
    }
}

However, I encountered the following error:

Uncaught TypeError: Object 0 has no method 'Update'

Oddly enough, the "InitializeRandom(...)" methods, added in the same manner, do work...

What am I missing here?

javascript arrays object

Answer 1

Answer №1

The issue you're facing is that the for in loop is not designed for iterating through arrays. It's specifically used for enumerating object properties.

Instead, you should opt for a standard for loop like this:

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

Answer 2

The issue you're facing is that the for in loop is not designed for iterating through arrays. It's specifically used for enumerating object properties.

Instead, you should opt for a standard for loop like this:

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

Answer 3

Answer №2

To properly set up your program, it is essential to initialize your variables:

function Rock() {
    this.size = 30.0;
    this.body = {};     //Begin with an object
    ...
}
var rocks = [];   //Start with an empty array
function GenerateNewRock() {
    ...

Furthermore, as rocks is an array, it is recommended to use a for loop for iteration:

function UpdateRocks()
{
    for(var i=0, l=rocks.length; i<l; i++)
    {
        var rock = rocks[i];
        rock.Update();
    }
}

Answer 4

To properly set up your program, it is essential to initialize your variables:

function Rock() {
    this.size = 30.0;
    this.body = {};     //Begin with an object
    ...
}
var rocks = [];   //Start with an empty array
function GenerateNewRock() {
    ...

Furthermore, as rocks is an array, it is recommended to use a for loop for iteration:

function UpdateRocks()
{
    for(var i=0, l=rocks.length; i<l; i++)
    {
        var rock = rocks[i];
        rock.Update();
    }
}

Unable to locate the JavaScript function

Answer №1

Answer №2

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