使用JS与Canvas实现动态吃豆人动画效果

<!DOCTYPE html>
<html>
<head lang="en">
 <meta charset="UTF-8">
 <title>吃豆人V01</title>
</head>
<body>
<canvas id="canvas" width="500px" height="500px" style="border: 1px solid black"></canvas>
<script>
 var canvas = document.getElementById("canvas");
 var context = canvas.getContext("2d");
 //TODO 面向对象方式解析
 //TODO 1.创建吃豆人的对象模板
 function Pacman(){
 //TODO 属性
 this.isOpen = true;//TODO 开关
 this.start = 45*Math.PI/180;
 this.end = 315*Math.PI/180;
 //TODO 方法
 //TODO 1.绘制方法
 this.paint = function(){
  //TODO 吃豆人的脸
  context.beginPath();
  context.arc(250,200,100,this.start,this.end);
  context.lineTo(250,200);
  context.closePath();
  context.fillStyle = "yellow";
  context.fill();
  context.stroke();
  //TODO 吃豆人的眼睛
  context.beginPath();
  context.arc(250,150,15,0,Math.PI*2);
  context.fillStyle = "black";
  context.fill();
  //TODO 吃豆人的眼神
  context.beginPath();
  context.arc(255,145,5,0,Math.PI*2);
  context.fillStyle = "white";
  context.fill();
 }
 //TODO 2.控制开闭切换
 this.open = function(){
  if(this.isOpen){//TODO 开口
  this.start = 45*Math.PI/180;
  this.end = 315*Math.PI/180;
  this.isOpen = false;
  }else{//TODO 闭口
  this.start = 0;
  this.end = Math.PI*2;
  this.isOpen = true;
  }
 }
 }
 //TODO 创建吃豆人的对象
 var pacman = new Pacman();
 //TODO 核心控制器
 setInterval(function(){
 context.clearRect(0,0,canvas.width,canvas.height);
 pacman.paint();
 pacman.open();
 },200);
</script>
</body>
</html>