Conway's Game of Life - In Javascript

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Recently, someone mentioned to me Conway’s Game of Life was a programming challenge at a code retreat they attended. I had never heard of it so I went to take a look at the concept. It seemed like a cool idea. So, I decided to use Canvas and Javascript to create my own instance of it. This is just my first draft of it - so take a look. And, if I’ve done anything incorrectly, please please please! let me know.

The canvas was really simple:

``````<h1>Conway's Game of Life</h1>
<h2>Using Javascript and Canvas</h2>
<canvas width="500" id="mainBoard" height="500"></canvas>
``````

And now the javascript used in this document:

``````(function(){

/**
* Game of life object
*/
function GOL() {

/**
* the color of the on cells
* @type {String}
*/
const ON_COLOR = '#336699';

/**
* The canvas DOM element
* @private
*/
var _canvas;

/**
* Current Matrix
* @type {Array}
* @private
*/
var _currentMatrix = [];

/**
* Initializer function
* @public
*/
this.start = function() {
_canvas = document.getElementById('mainBoard');
_bigBang();
setInterval(function(){_watchEvolution()}, 100);
};

/**
* Generates the random pattern and paints it
* @private
*/
var _bigBang = function() {
var limit = 500;

for (var x = 0; x < limit; x++) {
_currentMatrix[x] = [];
for (var y = 0; y < limit; y++) {
_currentMatrix[x][y] = Math.round(Math.random());
}
}

_paintCurrentMatrix();
};

/**
* Kicks off the cycle, regenerating new matrix and repainting
* @private
*/
var _watchEvolution = function() {
_generateNewMatrix();
_clearCanvas();
_paintCurrentMatrix();
};

/**
* Generates a new matrix based on the currentMatrix and assigns it
* @private
*/
var _generateNewMatrix = function() {
var newMatrix = [];

for (var x = 0, xLimit = _currentMatrix.length; x < xLimit; x++) {
newMatrix[x] = [];
for (var y = 0, yLimit = _currentMatrix[0].length; y < yLimit; y++) {

var liveNeighborsCount = 0;

if (_currentMatrix[x-1] != undefined) {
if (_currentMatrix[x-1][y-1]) {
liveNeighborsCount++;
}
if (_currentMatrix[x-1][y]) {
liveNeighborsCount++;
}
if (_currentMatrix[x-1][y+1]) {
liveNeighborsCount++;
}
}

if (_currentMatrix[x][y-1]) {
liveNeighborsCount++;
}
if (_currentMatrix[x][y+1]) {
liveNeighborsCount++;
}

if (_currentMatrix[x+1] != undefined) {
if (_currentMatrix[x+1][y-1]) {
liveNeighborsCount++;
}
if (_currentMatrix[x+1][y]) {
liveNeighborsCount++;
}
if (_currentMatrix[x+1][y+1]) {
liveNeighborsCount++;
}
}

var pointValue = 0;

if (_currentMatrix[x][y]) {
// live
if (liveNeighborsCount == 2 || liveNeighborsCount == 3) {
pointValue = 1;
}
}
else {
if (liveNeighborsCount == 3) {
pointValue = 1;
}
}

newMatrix[x][y] = pointValue;
}
}

_currentMatrix = newMatrix;
};

/**
* Clears the canvas
* @private
*/
var _clearCanvas = function() {
var ctx = _canvas.getContext('2d');
ctx.clearRect(0,0,_canvas.width, _canvas.height);
}

/**
* Takes the current matrix and paints it to the canvas
* @private
*/
var _paintCurrentMatrix = function() {
var ctx = _canvas.getContext('2d');
ctx.fillStyle=ON_COLOR;

for (var x in _currentMatrix) {
for (var y in _currentMatrix[x]) {
if (_currentMatrix[x][y] == 1) {
ctx.fillRect(x, y, 1, 1);
}
}
}
};
};

var game = new GOL();
game.start();
})();
``````