JavaScript 实现小球沿正弦曲线运动

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>Title</title>
 <style>
 .dot{
 margin-top: 300px;
 position: absolute;
 width: 1px;
 height: 1px;
 background: #000000;
 }
 #ball{
 width: 10px;
 height: 10px;
 background: red;
 border: 1px solid red;
 position: absolute;
 border-radius: 10px;
 }
 </style>
</head>
<body>
 
<div style="position: relative; width: 600px;
height: 600px;
 border: 1px solid #000000" id="draw_bo" >
</div>
<div id="ball" ></div>
<script type="text/javascript">
 var dom=document.getElementById("draw_bo");
 var ball=document.getElementById("ball");
 var x=0,y=300;
 ball.style.left=x+"px";//小球初始坐标x
 ball.style.top=y+"px";//小球初始坐标y
 for(var angle=0;angle<600;angle+=0.01){//画正弦线
 var childDot=document.createElement('div');
 childDot.className='dot';
 childDot.style.top=300*(Math.sin(angle*Math.PI/300))+"px";
 childDot.style.left=angle+"px";
 dom.appendChild(childDot);
 }
 var time=setInterval(function () {
 x=x+5;//小球运动速度
 y=Math.floor(Math.sin(x/600*2*Math.PI)*300)+300;//小球运动的高度
 if(x>600) x=0;
 ball.style.left=x+"px";
 ball.style.top=y+"px";
 },100);
</script>
</body>
</html>