After copy and pasting your code I found a couple of things:
- You didn't add an event listener to anything, you should add it to something so I added it to document.
- You initialize the exposed array with values "false" and later check if they are false. These are not the same, the string "false" isn't the Boolean false.
- You initializes the exposed array as a multi dimensional array [[false,false,false ...]] this should be a single dimension array because later you check exposed[1] (1 depending on the mouse x position.
- No need to call draw and update every 16 milliseconds, you can call it after someone clicked.
- Wrapped the whole thing up in a function so there are no global variables created.
Here is the code after changing these obvious errors. There might be room for optimization but for now I've gotten the problems out.
<!DOCTYPE html>
<html>
<head>
<title>test</title>
</head>
<body>
<div id="game"></div>
<script type="text/javascript">
(function(){
//HTML5 Memory Game implementation
//main variables
var cards = [1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8];
var exposed = makeArray(false, 16);
var first_card = 0;
var second_card = 0;
var moves = 0;
var WIDTH = 800;
var HEIGHT = 100;
var state = 0;
var mouseX = 0;
var mouseY = 0;
//creating canvas
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = WIDTH;
canvas.height = HEIGHT;
document.getElementById("game").appendChild(canvas);
//filling empty array with number,character,object
function makeArray(value, length) {
var newArray = [];
var i = 0;
while (i < length) {
newArray.push(value);
i++;
}
return newArray;
}
//shuffling algorithm
function shuffle(array) {
var copy = [];
var n = array.length;
var i;
while (n) {
i = Math.floor(Math.random() * n--);
copy.push(array.splice(i, 1)[0]);
}
return copy;
}
//where user clicks
function getClickPosition(event) {
var X = event.pageX - canvas.offsetLeft;
var Y = event.pageY - canvas.offsetTop;
return mouse = [X, Y];
}
//read click position
function readPos(event) {
mousePos = getClickPosition(event);
mouseX = mousePos[0];
mouseY = mousePos[1];
update();
draw();
}
//initializing
function init() {
state = 0;
moves = 0;
exposed = makeArray(false, 16);
cards = shuffle(cards);
}
//drawing cards
function draw() {
ctx.clearRect(0, 0, WIDTH, HEIGHT);
for (var i in cards) {
if (exposed[i] === true) {
ctx.fillStyle = "rgb(150, 150, 150)";
ctx.font = "50px Courier New";
ctx.fillText(cards[i], (i * 50 + 12), 65);
} else {
ctx.strokeStyle = "rgb(250, 0, 0)";
ctx.fillStyle = "rgb(0, 0, 250)";
ctx.fillRect(i * 50, 0, 50, 100);
ctx.strokeRect(i * 50, 0, 50, 100);
}
}
};
//update cards
function update() {
if (exposed[parseInt(mouseX / 50)] === false) {
if (state == 0) {
state = 1;
first_card = parseInt(mouseX / 50);
exposed[parseInt(mouseX / 50)] = true;
} else if (state == 1) {
state = 2;
second_card = parseInt(mouseX / 50);
exposed[parseInt(mouseX / 50)] = true;
} else {
if (cards[first_card] != cards[second_card]) {
exposed[first_card] = false;
exposed[second_card] = false;
}
state = 1;
first_card = parseInt(mouseX / 50);
exposed[parseInt(mouseX / 50)] = true;
}
}
}
document.body.addEventListener('click', readPos, false);
init();
draw();
})();
</script>
</body>
</html>