Tutorial/BouncingBalls.html at master · Nicolas-Chourot/Tutorial · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Bouncing ball</title>
    <style>
        button {
            font-size: x-large;
            width:120px;
        }
        canvas{
            border:10px solid gray;
            margin: auto;
        }
    </style>
</head>
<body>
    <canvas id="drawingContext" width="800" height="800"> </canvas>
    <h2>
        <button id="btn_add">add ball</button>
        <button id="btn_start">start</button>
        <button id="btn_sound">sound off</button>
    </h2>

<script>

    class Point {
        constructor (x, y){
            this.x = x;
            this.y = y;
        }
    }

    class RGBA {
        constructor(r = 255, g = 255, b = 255, a = 1){
            this.r = r;
            this.g = g;
            this.b = b;
            this.a = a;
        }

        randomize () {
            this.r = Math.random()*255;
            this.g = Math.random()*255;
            this.b = Math.random()*255;
            this.a = Math.random()*0.5 +0.5;
            return this;
        }

        toString() {
            return "rgba(" + this.r + "," + this.g + "," + this.b + "," + this.a + ")";
        }
    }

    class Ball {
        constructor (position, direction, color, canvas, bouncingSoundURL) {
            this.position = position;
            this.direction = direction;
            this.canvas = canvas;
            this.color = color;
            this.bouncingSoundURL = bouncingSoundURL;
            this.sound = true;
            this.radius = 25;
        }

        bounce(direction){
            direction = - direction;

            if (this.sound) {
                let sound = new Audio(this.bouncingSoundURL);
                setTimeout(() => { sound.play(); }, 0);
            }

            let randomizeBounceDirection = ((Math.random() >= 0.5 ? 1 : -1) * Math.random()*1/100) * direction;
            let newDirection = randomizeBounceDirection + direction;

            return newDirection;
        }

        move() {
            this.position.x += this.direction.x;
            this.position.y += this.direction.y;

            if ((this.position.x <= this.radius/2) || (this.position.x > this.canvas.width - this.radius/2)) {
                this.direction.x = this.bounce(this.direction.x);
            }
            if ((this.position.y <= this.radius/2) || (this.position.y > this.canvas.height - this.radius/2)) {
                this.direction.y = this.bounce(this.direction.y);
            }
        }

        draw() {
            this.canvas.beginPath();
            this.canvas.ellipse(this.position.x, this.position.y, this.radius, this.radius, 0, 0, 2 * Math.PI);
            this.canvas.closePath();
            this.canvas.fillStyle = this.color.toString();
            this.canvas.fill();
        }
    }

    class Balls {
        constructor(canvas, bounceSoundURL){
            this.canvas = canvas;
            this.bounceSoundURL = bounceSoundURL;
            this.balls = [];
        }

        addRandomizedBall() {
            let ball = new Ball(new Point(this.canvas.width / 2, this.canvas.height / 2) /* position */,
                                new Point( Math.random() * 10 - 5 , Math.random() * 10 - 5)/* direction */,
                                new RGBA().randomize(), /* color */
                                this.canvas,
                                this.bounceSoundURL);
            ball.sound = soundActivated;
            ball.draw();
            this.balls.push(ball);
        }

        eraseCanvas() {
            this.canvas.beginPath();
            this.canvas.clearRect(0, 0, this.canvas.width, this.canvas.height);
            this.canvas.closePath();
        }

        move() {
            this.eraseCanvas();
            for(let ball of this.balls) {
                ball.move();
                ball.draw();
            }
        }

        set soundActivated (value) {
            for(let ball of this.balls) {
                ball.sound = value;
            }
        }
    }

    document.addEventListener('DOMContentLoaded', init_UI);

    let balls = null;
    let timerStarted = false;
    let soundActivated = false;
    let refresh_Interval = 10; /* miliseconds */

    function init_UI() {
        document.getElementById('btn_start').addEventListener('click', startStopTimer);
        document.getElementById('btn_add').addEventListener('click', addBall);
        document.getElementById('btn_sound').addEventListener('click', toogleSound);

        init_Balls();
    }

    function get_Canvas(id) {
        let canvasElem = document.getElementById(id);
        canvas = canvasElem.getContext('2d');
        canvas.width = canvasElem.width;
        canvas.height = canvasElem.height;
        return canvas;
    }

    function init_Balls() {
        let canvasCTX = get_Canvas('drawingContext');
        balls = new Balls(canvasCTX, 'Boing3.mp3');
        balls.addRandomizedBall();
    }

    function startStopTimer() {
        if (!timerStarted) {
            timerStarted = true;
            document.getElementById('btn_start').innerText = "stop";
            timerId = setInterval(()=>{ balls.move(); }, refresh_Interval);
        }  else {
            timerStarted = false;
            document.getElementById('btn_start').innerText = "start";
            clearTimeout(timerId);
            document.getElementById('btn_start').set
        }
    }

    function addBall() {
            balls.addRandomizedBall();
    }

    function toogleSound() {
        let btn_sound = document.getElementById('btn_sound');
        soundActivated = !soundActivated;

        if (!soundActivated)
            btn_sound.innerText = "sound off";
        else
            btn_sound.innerText = "sound on";

        balls.soundActivated = soundActivated;
    }

</script>
</body>
</html>