HTML5 做波形运动的小球

波形运动：

    var canvas=document.getElementById("ballBroad");
            var context=canvas.getContext("2d");
            //角度
            var angle=0;
            //Y步长
            var speedY=0.1;
            //x步长
            var speedX=3;
            //刷新频率
            var frames=1000/60;
            //球对象
            var Ball=function(radius,color,x,y)
            {
                this.radius=radius;
                this.color=color;
                this.x=x;
                this.y=y;
            }
            //中心点
            var centerX=canvas.width/2;
            var centerY=canvas.height/2;
            //存放小球走过的点
            var points=[];
            
            
            //创建一个球 
            var newBall=new Ball(20,"#ff000",0,centerY);
            
            //在画板中间绘制球 
            DrawBall(newBall);
            //存放
            points.push({x:newBall.x,y:newBall.y});
            
            
            //让球平稳的动起来
            var drawAsync = eval(Jscex.compile("async", function () {
                        while(true)
                        {
                            newBall.y=centerY+Math.sin(angle)*centerY;
                            newBall.x+=speedX;
                            if(newBall.x>canvas.width)
                            {
                                newBall.x=0;
                                points=[];
                            }
                            angle+=speedY;
                            DrawBall(newBall);
                            //存放小球的点
                            points.push({x:newBall.x,y:newBall.y});
                            
                            //绘制线条
                            DrawBallLine();
                            //每秒60次
                            $await(Jscex.Async.sleep(frames));
                        }                                
            }));
           drawAsync().start();
           
           function DrawBall(ball)
           {
               context.clearRect(0, 0, canvas.width, canvas.height);
               //在画板中间绘制球 
            context.beginPath();
            context.arc(ball.x, ball.y, newBall.radius, 0, 2 * Math.PI, false); 
            context.fillStyle = ball.color;
            context.fill();
            context.lineWidth = 5;
            context.strokeStyle = "#ff0000";
            context.stroke();
           }
           //绘制小球的移动轨迹
           function DrawBallLine()
           {
                    for(var i=0;i<points.length;i++)
                    {
                        if(i==0)
                        {
                            context.moveTo(points[i].x,points[i].y)
                        }
                        context.lineTo(points[i].x,points[i].y)
                        context.stroke();
                    }
           }