Canvas实现动态的雪花效果

效果如下：

代码如下：

<!DOCTYPE html>
<html>
<head>
 <meta charset="utf-8">
 <title>Canvas</title>
 <style type="text/css">
 *{
 margin: 0;
 padding: 0;
 }
 html, body{
 height: 100%;
 }
 #myCanvas{
 background-color: #87CEEB;
 }
 </style>
</head>
<body>
 <canvas id="myCanvas" width="1000" height="600">您的浏览器不支持Canvas元素</canvas>
 <script type="text/javascript">
 var canvas = document.getElementById("myCanvas");
 var context = canvas.getContext("2d");
 var practicles = [];
 for (var i = 0; i < 500; i++) {//循环生成500粒
 practicles.push({
 x: Math.random()*(window.innerWidth),
 y: Math.random()*(window.innerHeight),
 vx: Math.random()-0.5,
 vy: Math.random()+0.5,
 size: Math.random()*3+1,
 color: "#FFF"
 })
 }
 function timeUpdate(){
 context.clearRect(0,0,window.innerWidth,window.innerHeight);//清除画布区域
 var practicle;
 for (var i = 0; i < 500; i++) {
 var practicle = practicles[i];
 practicle.x += practicles[i].vx;
 practicle.y += practicles[i].vy;
 if (practicle.x<0) {practicle.x=window.innerWidth}
 if (practicle.x>window.innerWidth) {practicle.x=0}
 if (practicle.y>window.innerHeight) {practicle.y=0}
 context.beginPath();
 context.arc(practicle.x,practicle.y,practicle.size,0,Math.PI*2)
 context.closePath();
 context.fillStyle = practicle.color;
 context.fill();
 }
 }
 setInterval(timeUpdate,40);
 </script>
</body>
</html>

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