Javascript Array Access undefined

Question

I am totally new to javascript, but I can program in Java, C# etc. already.

I want to generate a card deck, and after that I want to access this array of cards.

function Card(rank, suit)
{
    this.rank = rank;
    this.suit = suit;
}

function Deck()
{
    this.ranks = new Array("A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K");
    this.suits = new Array("Hearts", "Clubs", "Diamonds", "Spades");
    this.cards = Array(52);
    this.makeDeck = function()
    {
        console.log("Executed MakeDeck!");
        for(var i = 0; i < this.suits.length; i++)
        {
            for(var j = 0; j < this.ranks.length; j++)
            {
                this.cards.push(new Card(this.ranks[j],this.suits[i]));
            }
        }
    }
}

function btnClick()
{
    var deck = new Deck();
    deck.makeDeck();
    console.log(deck.cards[0]);
}

In the function "btnClick()" I want to log the first item in the array, but the console just tells my "undefined". I can't find my mistake, maybe you can help me?

-hisses like a cat- Don't use new Array()! Use array literals: ["A","2",...]; — Niet the Dark Absol
– Niet the Dark Absol, Commented May 25, 2014 at 22:47
@Juhana Ah, too true! I didn't realise the internal pointer was positioned at the end of the array when using the length constructor — Phil
– Phil, Commented May 25, 2014 at 22:50
Bioaim - Learn to use your browser's debugging tool. This will help you identify problems like this in the future. — Lee Taylor
– Lee Taylor, Commented May 25, 2014 at 23:01

Niet the Dark Absol · Accepted Answer · 2014-05-25 22:48:55Z

4

The problem is that you have initialised an array with 52 elements... and you are then pushing more elements onto it.

What you need to do is just have this.cards = [];. JavaScript has variable-length arrays.

answered May 25, 2014 at 22:48

Niet the Dark Absol

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3 Comments

Josh Beam Over a year ago

"JavaScript has variable-length arrays." <-- very important distinction

Bergi Over a year ago

Not 52 elements actually. Just a .length of 52, it's a sparse array.

Bioaim Over a year ago

thank you very much, it works now.. but i don't push more then 52 elements in the array. its length is actually 52.

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