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?

• Niet the Dark Absol: -hisses like a cat- Don't use new Array()! Use array literals: ["A","2",...];
• Phil: @NiettheDarkAbsol Does it really matter?
• JJJ: @Phil In this case it's the cause of the problem.
• Phil: @Juhana Ah, too true! I didn't realise the internal pointer was positioned at the end of the array when using the length constructor
• Lee Taylor: Bioaim - Learn to use your browser's debugging tool. This will help you identify problems like this in the future.

Answer 1

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.

• Josh Beam: "JavaScript has variable-length arrays." <-- very important distinction
• Bergi: Not 52 elements actually. Just a .length of 52, it's a sparse array.
• Bioaim: thank you very much, it works now.. but i don't push more then 52 elements in the array. its length is actually 52.