game_using_constructor.js

/**
 * Here is another way to do the Game constructor. This is the traditional JS way of doing constructor functions
 * The benefits are that this is the fastest way to construct and run a function. The downside is that all methods
 * and properties are publicly available, which is a gross way to design classes. Also, you are still forced to
 * often use .bind() in order to make the context is correct. But, regardless, if you look at many JS libraries,
 * this is how you will find their classes structured.
 * 
 * To run the constructor and instantiate the class:
 * var game = new Game({
 *     levels: levels,
 *     ctx : canvas.getContext("2d"),
 *     tileSize : 16
 * });
 **/
 
var EventEmitter = require("events").EventEmitter;

function Game(options) {
    this.defaultGrid = options.levels;
    this.grid = this.cloneLevels(options.levels);
    this.canvas = options.canvas;
    this.ctx = options.ctx;
    this.tileSize = options.tileSize;
    this.events = new EventEmitter();
}

Game.prototype.frozen = false;
Game.prototype.currentLevel = 0;
Game.prototype.charX = 1;
Game.prototype.charY = 1;
Game.prototype.moveQueue = [];
Game.prototype.tiles = {
    0: "black",
    1: "yellow",
    2: "blue",
    3: "red"
};

Game.prototype.draw = function() {
    if(!this.frozen && this.moveQueue.length > 0) {
        this.moveQueue[0]();
    }
    this.moveQueue = [];
    this.make();
};

Game.prototype.make = function() {
    var level = this.currentLevel;
    this.grid[level][this.charX][this.charY] = 2;
    var ctx = this.ctx;
    var tileSize = this.tileSize;
    var row, col;
    for (var i = 0; i < this.grid[level].length; i++) {
        row = tileSize * i;
        for (var j = 0; j < this.grid[level][0].length; j++) {
            col = tileSize * j;
            ctx.beginPath();
            ctx.rect(row, col, tileSize, tileSize);
            ctx.fillStyle = this.tiles[this.grid[level][i][j]];
            ctx.fill();
            ctx.closePath();
        }
    }
};

Game.prototype.moveRight = function() {
    var level = this.currentLevel;
    if(this.charX < 19) {
        if (this.grid[level][this.charX + 1][this.charY] === 0) {
            this.grid[level][this.charX][this.charY] = 0;
            this.charX += 1;
            this.grid[level][this.charX][this.charY] = 2;
        } else if (this.grid[level][this.charX + 1][this.charY] === 3) {
            this.levelUp();
        }
    }
};

Game.prototype.moveLeft = function() {
    var level = this.currentLevel;
    if(this.charX > 0) {
        if (this.grid[level][this.charX - 1][this.charY] === 0) {
            this.grid[level][this.charX][this.charY] = 0;
            this.charX -= 1;
            this.grid[level][this.charX][this.charY] = 2;
        } else if (this.grid[level][this.charX - 1][this.charY] === 3) {
            this.levelUp();
        }
    }
};

Game.prototype.moveUp = function() {
    var level = this.currentLevel;
    if(this.charY > 0) {
        if (this.grid[level][this.charX][this.charY -1] === 0) {
            this.grid[level][this.charX][this.charY] = 0;
            this.charY -= 1;
            this.grid[level][this.charX][this.charY] = 2;
        } else if (this.grid[level][this.charX][this.charY -1] === 3) {
            this.levelUp();
        }
    }
};

Game.prototype.moveDown = function() {
    var level = this.currentLevel;
    if(this.charY < 19) {
        if (this.grid[level][this.charX][this.charY + 1] === 0) {
            this.grid[level][this.charX][this.charY] = 0;
            this.charY += 1;
            this.grid[level][this.charX][this.charY] = 2;
        } else if (this.grid[level][this.charX][this.charY + 1] === 3) {
            this.levelUp();
        }
    }
};

Game.prototype.levelUp = function() {
    this.moveQueue = [];
    if (this.currentLevel === this.grid.length - 1) {
        this.frozen = true;
        this.events.emit("gameOver");
    } else {
        this.frozen = true;
        this.currentLevel++;
        this.events.emit("leveledUp", {currentLevel: this.currentLevel + 1});
        this.charX = 1;
        this.charY = 1;
        this.frozen = false;
    }
};

Game.prototype.restart = function() {
    this.events.emit("restart");
    this.grid = this.cloneLevels(this.defaultGrid);
    this.charX = 1;
    this.charY = 1;
    this.currentLevel = 0;
    this.frozen = false;
    this.moveQueue = 0;
    this.make();
};

Game.prototype.keyDownHandler = function(e) {
    switch(e.keyCode) {
        case 39:
        this.moveQueue.push(this.moveRight.bind(this));
        break;
        case 37:
        this.moveQueue.push(this.moveLeft.bind(this));
        break;
        case 38:
        this.moveQueue.push(this.moveUp.bind(this));
        break;
        case 40:
        this.moveQueue.push(this.moveDown.bind(this));
        break;
    }
};

Game.prototype.cloneLevels = function(levels) {
    return levels.map(function(level) {
        return level.map(function(row) {
            return row.concat();
        });
    });
};

Game.prototype.start = function() {
    document.addEventListener("keydown", this.keyDownHandler.bind(this));
    this.interval = setInterval((function() {
        this.draw();
    }).bind(this), 90);
    return this;
};

module.exports = Game;