Code example of using canvas to implement pinball

nbsp;html>


    <meta>
    <title>弹球</title>
    <script></script>


<canvas></canvas>
<script>
    // 全局canvas
    let canvas = document.getElementById("canvas");
    let context = canvas.getContext("2d");
    // 弹球对象
    class Ball{
        x = 100;
        y = 40;
        xSpeed = -2;
        ySpeed = -2;
        constructor(){};
        getX(){
            return this.x;
        }
        getY(){
            return this.y;
        }
        setX(x){
            this.x = x;
        }
        setY(y){
            this.y = y;
        }
        getXSpeed(){
            return this.xSpeed;
        }
        setXSpeed(xSpeed){
            this.xSpeed = xSpeed;
        }
        getYSpeed(){
            return this.ySpeed;
        }
        setYSpeed(ySpeed){
            this.ySpeed = ySpeed;
        }
        // 绘制小球的方法
        draw = () => {
            context.beginPath();
            context.arc(this.x, this.y, 10, 0, Math.PI * 2, false);
            context.strokeRect(0, 0, 400, 400);
            context.fill();
        };
        // 移动操作
        move = () => {
            this.x = this.x + this.xSpeed;
            this.y = this.y + this.ySpeed;
        };
        // 边缘检测,碰撞检测
        checkCanvas = (panel) => {
            // 左右
            if(this.x < 5 || this.x > 400 - 5){
                this.xSpeed = -this.xSpeed;
            }
            // 上方
            if(this.y < 0){
                this.ySpeed = -this.ySpeed;
            }
            // 下方
            // 碰到挡板

            if(this.y > 390 - 10){
                if(this.x > panel.x && this.x < panel.xSize + panel.x){
                    this.ySpeed = -this.ySpeed;
                }else{
                    alert("游戏结束");
                    this.x = 100;
                    this.y = 10;
                }
            }
        }
    }
    // 增加一个挡板对象
    class Panel{
        constructor(){};
        // 左x
        x = 200;
        // 左y
        y = 390;
        // 长度
        xSize = 50;
        // 宽度
        ySize = 5;
        draw(){
            context.fillRect(this.x, this.y, this.xSize, this.ySize);
        }
    }
    // 创建出一个小球对象
    let ball = new Ball();
    // 创建出挡板对象
    let panel = new Panel();
    // 每10秒为一帧
    window.setInterval(() => {
        // 清空画布
        context.clearRect(0, 0, 400, 400);
        // 画出小球
        ball.draw();
        // 画出挡板
        panel.draw();
        // 移动
        ball.move();
        // 进行边界判断
        ball.checkCanvas(panel);
    },10);
    // 控制挡板
    $("body").keydown((event) => {
        if(event.keyCode == 37){
            panel.x = panel.x - 5;
            // 移出边界问题处理
            if(panel.x < 0){
                panel.x = 0;
            }
        }
        if(event.keyCode == 39){
            panel.x = panel.x + 5;
            // 移出边界处理
            if(panel.x + panel.xSize > 400){
                panel.x = 400 - panel.xSize;
            }
        }
    })
</script>