这段代码是一个HTML5 Canvas动画，它通过JavaScript创建了一个动态的爱心效果。页面初始化时，首先定义了一些基本设置，如粒子数量、持续时间、速度等。然后，定义了Point和Particle类，用于处理粒子的位置和运动。接着，使用ParticlePool管理粒子池，实现粒子的循环利用。
核心动画逻辑在`render`函数中，这个函数会在每一帧调用`requestAnimationFrame`来更新和渲染粒子。动画效果通过在Canvas上绘制粒子来实现，粒子从爱心形状的路径上发射出来，随着时间逐渐消失，形成了一个连续的动态效果。
此外，还有一个`pointOnHeart`函数用于生成爱心形状的路径点，以及一个辅助函数用于创建粒子图像。整个动画在全屏黑色背景上运行。
整体来看，这段代码展示了如何使用HTML5 Canvas和JavaScript来创建复杂的动画效果，适合用于网页装饰或特殊场合的视觉效果展示。
<!DOCTYPE html>
<html>
<head>
<title></title>
</head>
<style>
* {
padding: 0;
margin: 0;
}
html,
body {
height: 100%;
padding: 0;
margin: 0;
background: #000;
}
canvas {
position: absolute;
width: 100%;
height: 100%;
}
.aa {
position: fixed;
/* 固定位置 */
left: 50%;
/* 向左移动自身宽度的50% */
transform: translateX(-50%);
/* 向左移动自身宽度的50%，实现水平居中 */
top: 45%;
color: #ccc;
/* 文字颜色设置为灰色 */
font-family: Arial, sans-serif;
/* 设置字体 */
font-size: 30px;
/* 设置字体大小 */
}
</style>
<body>
<canvas id="pinkboard"></canvas>
<div class="aa">美羊羊</div> <!-- 名字 -->
<script>
/*
* 设置动画参数
*/
var settings = {
particles: {
length: 500, // 粒子的最大数量
duration: 2, // 粒子存在的时间（秒）
velocity: 100, // 粒子的速度（像素/秒）
effect: -0.75, // 控制粒子运动效果的参数
size: 30 // 粒子的大小（像素）
},
};
/*
* RequestAnimationFrame polyfill by Erik M?ller
*/
(function () { var b = 0; var c = ["ms", "moz", "webkit", "o"]; for (var a = 0; a < c.length && !window.requestAnimationFrame; ++a) { window.requestAnimationFrame = window[c[a] + "RequestAnimationFrame"]; window.cancelAnimationFrame = window[c[a] + "CancelAnimationFrame"] || window[c[a] + "CancelRequestAnimationFrame"] } if (!window.requestAnimationFrame) { window.requestAnimationFrame = function (h, e) { var d = new Date().getTime(); var f = Math.max(0, 16 - (d - b)); var g = window.setTimeout(function () { h(d + f) }, f); b = d + f; return g } } if (!window.cancelAnimationFrame) { window.cancelAnimationFrame = function (d) { clearTimeout(d) } } }());
/*
* 点(Point)类，用于处理二维空间中的点
*/
var Point = (function () {
function Point(x, y) {
this.x = (typeof x !== 'undefined') ? x : 0;
this.y = (typeof y !== 'undefined') ? y : 0;
}
Point.prototype.clone = function () {
return new Point(this.x, this.y);
};
Point.prototype.length = function (length) {
if (typeof length == 'undefined')
return Math.sqrt(this.x * this.x + this.y * this.y);
this.normalize();
this.x *= length;
this.y *= length;
return this;
};
Point.prototype.normalize = function () {
var length = this.length();
this.x /= length;
this.y /= length;
return this;
};
return Point;
})();
/*
* 粒子(Particle)类，用于创建和管理动画中的粒子
*/
var Particle = (function () {
function Particle() {
this.position = new Point();
this.velocity = new Point();
this.acceleration = new Point();
this.age = 0;
}
Particle.prototype.initialize = function (x, y, dx, dy) {
this.position.x = x;
this.position.y = y;
this.velocity.x = dx;
this.velocity.y = dy;
this.acceleration.x = dx * settings.particles.effect;
this.acceleration.y = dy * settings.particles.effect;
this.age = 0;
};
Particle.prototype.update = function (deltaTime) {
this.position.x += this.velocity.x * deltaTime;
this.position.y += this.velocity.y * deltaTime;
this.velocity.x += this.acceleration.x * deltaTime;
this.velocity.y += this.acceleration.y * deltaTime;
this.age += deltaTime;
};
Particle.prototype.draw = function (context, image) {
function ease(t) {
return (--t) * t * t + 1;
}
var size = image.width * ease(this.age / settings.particles.duration);
context.globalAlpha = 1 - this.age / settings.particles.duration;
context.drawImage(image, this.position.x - size / 2, this.position.y - size / 2, size, size);
};
return Particle;
})();
/*
* 粒子池(ParticlePool)类，用于高效管理大量粒子
*/
var ParticlePool = (function () {
var particles,
firstActive = 0,
firstFree = 0,
duration = settings.particles.duration;
function ParticlePool(length) {
// create and populate particle pool
particles = new Array(length);
for (var i = 0; i < particles.length; i++)
particles[i] = new Particle();
}
ParticlePool.prototype.add = function (x, y, dx, dy) {
particles[firstFree].initialize(x, y, dx, dy);
// handle circular queue
firstFree++;
if (firstFree == particles.length) firstFree = 0;
if (firstActive == firstFree) firstActive++;
if (firstActive == particles.length) firstActive = 0;
};
ParticlePool.prototype.update = function (deltaTime) {
var i;
// update active particles
if (firstActive < firstFree) {
for (i = firstActive; i < firstFree; i++)
particles[i].update(deltaTime);
}
if (firstFree < firstActive) {
for (i = firstActive; i < particles.length; i++)
particles[i].update(deltaTime);
for (i = 0; i < firstFree; i++)
particles[i].update(deltaTime);
}
// remove inactive particles
while (particles[firstActive].age >= duration && firstActive != firstFree) {
firstActive++;
if (firstActive == particles.length) firstActive = 0;
}
};
ParticlePool.prototype.draw = function (context, image) {
// draw active particles
if (firstActive < firstFree) {
for (i = firstActive; i < firstFree; i++)
particles[i].draw(context, image);
}
if (firstFree < firstActive) {
for (i = firstActive; i < particles.length; i++)
particles[i].draw(context, image);
for (i = 0; i < firstFree; i++)
particles[i].draw(context, image);
}
};
return ParticlePool;
})();
/*
* 动画的主要逻辑
*/
(function (canvas) {
var context = canvas.getContext('2d'),
particles = new ParticlePool(settings.particles.length),
particleRate = settings.particles.length / settings.particles.duration, // particles/sec
time;
// 根据给定的参数t，计算爱心形状上的点
function pointOnHeart(t) {
return new Point(
160 * Math.pow(Math.sin(t), 3),
130 * Math.cos(t) - 50 * Math.cos(2 * t) - 20 * Math.cos(3 * t) - 10 * Math.cos(4 * t) + 25
);
}
// 创建粒子图像，用于在动画中显示
var image = (function () {
var canvas = document.createElement('canvas'),
context = canvas.getContext('2d');
canvas.width = settings.particles.size;
canvas.height = settings.particles.size;
// helper function to create the path
function to(t) {
var point = pointOnHeart(t);
point.x = settings.particles.size / 2 + point.x * settings.particles.size / 350;
point.y = settings.particles.size / 2 - point.y * settings.particles.size / 350;
return point;
}
// create the path
context.beginPath();
var t = -Math.PI;
var point = to(t);
context.moveTo(point.x, point.y);
while (t < Math.PI) {
t += 0.01; // baby steps!
point = to(t);
context.lineTo(point.x, point.y);
}
context.closePath();
// create the fill
context.fillStyle = '#ea80b0';
context.fill();
// create the image
var image = new Image();
image.src = canvas.toDataURL();
return image;
})();
// 渲染函数，用于每一帧的动画绘制
function render() {
// next animation frame
requestAnimationFrame(render);
// update time
var newTime = new Date().getTime() / 1000,
deltaTime = newTime - (time || newTime);
time = newTime;
// clear canvas
context.clearRect(0, 0, canvas.width, canvas.height);
// create new particles
var amount = particleRate * deltaTime;
for (var i = 0; i < amount; i++) {
var pos = pointOnHeart(Math.PI - 2 * Math.PI * Math.random());
var dir = pos.clone().length(settings.particles.velocity);
particles.add(canvas.width / 2 + pos.x, canvas.height / 2 - pos.y, dir.x, -dir.y);
}
// update and draw particles
particles.update(deltaTime);
particles.draw(context, image);
}
// 处理Canvas大小变化的函数
function onResize() {
canvas.width = canvas.clientWidth;
canvas.height = canvas.clientHeight;
}
window.onresize = onResize;
// 延迟启动渲染，确保页面元素加载完毕
setTimeout(function () {
onResize();
render();
}, 10);
})(document.getElementById('pinkboard'));
</script>
</body>
</html>效果图：
![HTML+CSS+JS实现商城首页[web课设代码+模块说明+效果图]](https://i-blog.csdnimg.cn/direct/41f0acdef9e64987abfa53283973f387.png)
