Card-fighting game Part 2

var sounds = {
  block: new Audio('sounds/block.mp3'),
  dodge: new Audio('sounds/dodged.mp3'),
  sword: new Audio('sounds/sword.mp3')
};

sounds.sword.play(); // usage

function createPlayer(name, maxLife) { // factory functions
  var player = {
    name: name,
    life: maxLife,
    deck: undefined // no cards yet
  };

  return player;      
}

var player = createPlayer(undefined, 25); // usage
var computer = createPlayer("Hunter", 25);

function createDeck(array) {
  var cards = array; // private variable

  return {
    // removes the card off the top of the deck
    draw: function () {
      return cards.pop(); // the backside of the array the top of the deck
    },

    // returns the value of the card on the top of the deck
    peek: function () {
      return cards[cards.length - 1];
    },

    // returns the size of the deck
    size: function () {
      return cards.length;
    },

    // randomizes the order of the cards in the deck
    shuffle: function () {
      cards = shuffle(cards); // call your global shuffle function
    },

    // returns an array to be assigned to two players. Second array get's the extra card if the deck's length is odd
    deal: function () {
      var half = Math.floor(cards.length / 2);
      var deck0 = createDeck(cards.slice(0, half));
      var deck1 = createDeck(cards.slice(half));

      return [deck0, deck1];
    },

    // returns a string of the deck
    toString: function () {
      return cards.toString();
    }
  };
}

var deck = createDeck([1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8];
deck.shuffle();

var hands = deck.deal();
player.deck = hands[0];
computer.deck = hands[1];

function whoWon() {
    "use strict";
    var playerCard = player.deck.draw();
    var computerCard = computer.deck.draw();

    document.getElementById('computerDamageImage').setAttribute('src', 'images/empty.png');
    document.getElementById('playerDamageImage').setAttribute('src', 'images/empty.png');

    if (playerCard > computerCard) {
        computerLife = computerLife - (playerTopCard - computerTopCard);
        sounds.sword.play();
        document.getElementById('computerDamageImage').setAttribute('src', 'images/damage.gif');
        playerFeedback.innerHTML = computer.name + ' lost: ' + (playerTopCard - computerTopCard) + ' HP';
    } else if (playerCard < computerCard) {
        playerlife = playerlife - (computerTopCard - playerTopCard);
        sounds.sword().play();
        document.getElementById('playerDamageImage').setAttribute('src', 'images/damage.gif');
        playerFeedback.innerHTML = playerName + ' lost: ' + (computerTopCard - playerTopCard) + ' HP';
    } else {
        sounds.block.play();
        playerFeedback.innerHTML = 'It was a tie!';
    }
    checkIsGameOver();
}

// Returns first element that matches CSS selector {expr}.
// Querying can optionally be restricted to {container}’s descendants
function $(expr, container) {
    return typeof expr === "string"? (container || document).querySelector(expr) : expr || null;
}

// Returns all elements that match CSS selector {expr} as an array.
// Querying can optionally be restricted to {container}’s descendants
function $$(expr, container) {
    return [].slice.call((container || document).querySelectorAll(expr));
}