canvas.js

var myGamePiece;
var myObstacles = [];
var myScore;

function startGame() {
    myGamePiece = new component(30, 30, "red", 10, 120);
    myScore = new component("20px", "Consolas", "black", 0, 20, "text");
    myGameArea.start();
}

function restartGame() {
    document.getElementById("restartFilter").style.display = "none";
    document.getElementById("restartButton").style.display = "none";
    myGameArea.stop();
    myGameArea.clear();
    myGamePiece = {};
    myObstacles = [];
    myscore = {};
    document.getElementById("canvasGame").remove();
    startGame();
}

var myGameArea = {
    start: function () {
        this.canvas = document.createElement("canvas");
        this.canvas.setAttribute("id", "canvasGame");
        this.canvas.width = 480;
        this.canvas.height = 270;
        this.context = this.canvas.getContext("2d");
        document.getElementById("canvasContainer").appendChild(this.canvas);
        this.frameNo = 0;
        this.interval = setInterval(updateGameArea, 20);
        //keyboard controllers
        window.addEventListener('keydown', function (e) {
            myGameArea.keys = (myGameArea.keys || []);
            myGameArea.keys[e.keyCode] = true;
        });
        window.addEventListener('keyup', function (e) {
            myGameArea.keys[e.keyCode] = false;
        });
    },
    clear: function () {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    },
    stop: function () {
        clearInterval(this.interval);
    }
};

function component(width, height, colour, x, y, type) {
    this.type = type;
    this.width = width;
    this.height = height;
    this.speedX = 0;
    this.speedY = 0;
    this.x = x;
    this.y = y;
    this.update = function() {
        ctx = myGameArea.context;
        if (this.type === "text") {
            ctx.font = this.width + " " + this.height;
            ctx.fillStyle = colour;
            ctx.fillText(this.text, this.x, this.y);
        } else {
            ctx.fillStyle = colour;
            ctx.fillRect(this.x, this.y, this.width, this.height);
        }
    };
    this.newPos = function () {
        this.x += this.speedX;
        this.y += this.speedY;
    };
    this.crashWith = function (otherobj) {
        var myleft = this.x;
        var myright = this.x + (this.width);
        var mytop = this.y;
        var mybottom = this.y + (this.height);
        var otherleft = otherobj.x;
        var otherright = otherobj.x + (otherobj.width);
        var othertop = otherobj.y;
        var otherbottom = otherobj.y + (otherobj.height);
        var crash = true;
        if ((mybottom < othertop) || (mytop > otherbottom) || (myright < otherleft) || (myleft > otherright)) {
            crash = false;
        }
        return crash;
    };
}

function updateGameArea() {
    var x, y;
    for (i = 0; i < myObstacles.length; i += 1) {
        if (myGamePiece.crashWith(myObstacles[i])) {
            myGameArea.stop();
            document.getElementById("restartFilter").style.display = "block";
            document.getElementById("restartButton").style.display = "block";
            return;
        }
    }
    myGameArea.clear();
    myGameArea.frameNo += 1;
    if (myGameArea.frameNo === 1 || everyinterval(50)) {
        x = myGameArea.canvas.width;
        minHeight = 20;
        maxHeight = 200;
        height = Math.floor(Math.random()*(maxHeight-minHeight+1)+minHeight);
        minGap = 50;
        maxGap = 200;
        gap = Math.floor(Math.random()*(maxGap-minGap+1)+minGap);
        myObstacles.push(new component(10, height, "green", x, 0));
        myObstacles.push(new component(10, x - height - gap, "green", x, height + gap));
    }
    for (i = 0; i < myObstacles.length; i += 1) {
        myObstacles[i].x += -3;
        myObstacles[i].update();
    }
    //keyboard controllers
    myGamePiece.speedX = 0;
    myGamePiece.speedY = 0;
    if (myGameArea.keys && myGameArea.keys[37]) {myGamePiece.speedX = -3; }
    if (myGameArea.keys && myGameArea.keys[39]) {myGamePiece.speedX = 3; }
    if (myGameArea.keys && myGameArea.keys[38]) {myGamePiece.speedY = -3; }
    if (myGameArea.keys && myGameArea.keys[40]) {myGamePiece.speedY = 3; }
    myScore.text = "SCORE: " + myGameArea.frameNo;
    myScore.update();
    myGamePiece.newPos();
    myGamePiece.update();
}

function everyinterval(n) {
    return (myGameArea.frameNo / n) % 1 === 0;
}

// function moveup() {
//     myGamePiece.speedY -= 1;
// }
//
// function movedown() {
//     myGamePiece.speedY += 1;
// }
//
// function moveleft() {
//     myGamePiece.speedX -= 1;
// }
//
// function moveright() {
//     myGamePiece.speedX += 1;
// }
//
// function stopMove() {
//     myGamePiece.speedX = 0;
//     myGamePiece.speedY = 0;
// }