Pushing new function into an array - Javascript

Question

I cannot get this to work:

var global_variables = {
    players: []
}; 

var player = function(properties){
    this.width = properties.width;                            
    this.height = properties.height;
    this.position = properties.position;
    this.position.x = properties.position.x;
    this.position.y = properties.position.y;
}

function load_players(){
    global_variables.players.push(
        [
            new player(
                {
                    width: 10,
                    height: 10,
                    position: {
                        x: 50,
                        y: 50
                    },
                    colour: '#ff0000'
                }
            )
        ]
    );
}


 function init(){ 
    var ctx = load_canvas();
    load_players();

    for(a in global_variables.players){
        var _this = global_variables.players[a];
        alert(_this.colour);
    }
}

alert(_this.colour) just alerts undefined. Any ideas?

I updated the code to represent where i would call it... And again. hehe — Jimmyt1988
– Jimmyt1988, Commented Sep 17, 2012 at 21:33

dontGoPlastic · Accepted Answer · 2012-09-17 21:39:27Z

You were trying to loop before calling init
You were pushing your player instance wrapped in an array. You just wanted to push the player.
Don't use for ... in ... on an array. Use a regular loop or use forEach like I did.
You were never actually setting the colour property to your instance.

http://jsfiddle.net/GLsR2/

Here's the code from the fiddle:

var global_variables = {
    players: []
}; 

var player = function(properties){
    this.width = properties.width;                            
    this.height = properties.height;
    this.position = properties.position;
    this.position.x = properties.position.x;
    this.position.y = properties.position.y;
    this.colour = properties.colour;
}

function load_players(){
    global_variables.players.push(
        new player(
                {
                    width: 10,
                    height: 10,
                    position: {
                        x: 50,
                        y: 50
                    },
                    colour: '#ff0000'
                }
            )
      );
}


init();

global_variables.players.forEach(function(player) {
   alert(player.colour); 
});

function init(){ 
    load_players();
}

nnnnnn · Accepted Answer · 2012-09-17 21:38:23Z

2

You get undefined from _this.colour for two reasons:

You don't set a colour property in your constructor
Rather than pushing each new player into the array you are pushing a one-element array containing the new player. That is, you're creating an array of arrays.

Add this to the constructor:

    this.colour = properties.colour;

And then remove the square brackets from in the load_players() function:

function load_players(){
    global_variables.players.push(        
            new player({
                    width: 10,
                    height: 10,
                    position: {
                        x: 50,
                        y: 50
                    },
                    colour: '#ff0000'
            })
    );
}

Demo: http://jsfiddle.net/ZACnC/

answered Sep 17, 2012 at 21:38

nnnnnn

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2 Comments

Jimmyt1988 Over a year ago

Oh god.. the colour not being set.. how embarrassing.. thank you so much for taking the time to out my noobish school boy error of being a noob. toolateforcode.com

Jimmyt1988 Over a year ago

I changed it to: global_variables.players = [ new player(... Thanks once again

gen_Eric · Accepted Answer · 2012-09-17 21:37:56Z

When you are pushing on to global_variables.players, you are pushing an array containing the new Player object, not the object itself.

You don't need the [] when using .push.

function load_players(){
    global_variables.players.push(
        new player({
            width: 10,
            height: 10,
            position: {
                x: 50,
                y: 50
            },
            colour: '#ff0000'
        })
    );
}

P.S. Don't use for...in for arrays. Just use a normal for.

for(var a = 0, len = global_variables.players.length; a < len; a++){
    var _this = global_variables.players[a];
    alert(_this.colour);
}

P.P.S. You need to add this.colour = properties.colour; to your player constructor.

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