这个也是别人的代码，就不多介绍了
写了些注释
body {
overflow:hidden;
margin:0;
padding:0;
background-color:#222222
}
</style>
</head>
<body>
<canvas id="canvasParticle">Canvas is not supported in your brower.</canvas><script>
window.onload = function() {
var oCanvas = document.getElementById('canvasParticle');
var cxt = null;
//用来存放粒子的素组
var particles = {};
var particleIndex = 0;
if (oCanvas.getContext) {
cxt = oCanvas.getContext('2d');
}
oCanvas.width = window.innerWidth;
oCanvas.height = window.innerHeight;
function Particle() {
particleIndex++;
particles[particleIndex] = this;
//粒子放射的中心点
this.x = oCanvas.width / 2;
this.y = oCanvas.height / 2;
//初始化粒子沿X轴和Y轴的速度
this.vx = Math.random() * 6 - 3;
this.vy = Math.random() * 4 - 2;
this.growth = (Math.abs(this.vx) + Math.abs(this.vy)) * 0.01; // 根据x/y轴的位置决定大小
this.id = particleIndex;
this.size = 0;
this.color = getRandomColor();
};
Particle.prototype.draw = function() {
this.x += this.vx;
this.y += this.vy;
//根据移动的距离逐渐变大
this.size += this.growth;
if (this.x < 0 || this.x > oCanvas.width || this.y < 0 || this.y > oCanvas.height) {
//出界则移除
delete particles[this.id];
}
cxt.fillStyle = this.color;
cxt.beginPath();
cxt.arc(this.x, this.y, this.size, 0, 2 * Math.PI);
cxt.fill();
};
function animate() {
requestAnimationFrame(animate);
cxt.fillStyle = '#222222';
cxt.fillRect(0, 0, oCanvas.width, oCanvas.height);
//每次网数组添加一个数据
new Particle();
//遍历数组，依次画出
for (var i in particles) {
particles[i].draw();
}
};
requestAnimationFrame(animate);
};
//随机颜色方法
function getRandomColor() {
return '#' + (Math.random() * 0xffffff << 0).toString(16);
};</script>
</body>