【前端小案例】浪漫动态爱心

爱心

1. 案例简介
2. 爱心实现
- 2.1 盒子模型
- 2.2 CSS样式
- 2.3 JS实现动效
3. 完整源码

1. 案例简介

最近网剧《点燃我，温暖你》热映，相信广大男同胞的女朋友都在吵着要李洵的❤，没有女朋友的兄弟也要注意，这机会它不就来了吗，博主在刷短视频时也看了部分剪辑，当时震惊我的是那句台词“这次老师布置的可是求三个数里的最大值，你不会是怕自己做不出来所以不敢交作业吧。”这句多少是有些搞笑了，后来也有刷到更新剧集的，就是C语言考试时，考试题目是打印爱心❤，男主写了个动态爱心❤，给女主看懵了，当时就有不祥的预感，果然下午就有人找我要我给她弄一个，C语言咱真做不到，前端的可以试试，这就来上！完整源码在最后，复制就可用(点击目录直接跳转）！
效果如图

2. 爱心实现

这个案例其实只是简单的一个盒子模型，关键是使用js让这个爱心实现动效，包括爱心边界要由许多跳动的小心心组成，以及在不断缩小实现跳动效果。

2.1 盒子模型

首先自然是一个盒子模型打底，在其中实现爱心的效果

<canvas id="pinkboard"></canvas>

2.2 CSS样式

CSS也比较简单，只是简单的边界修订，包括背景颜色（黑色），大小，宽高等等有的没的。

html, body {height: 100%;padding: 0;margin: 0;background: #000;
}
canvas {position: absolute;width: 100%;height: 100%;
}

2.3 JS实现动效

这个就比较复杂啦，包括动效的方向，动效范围，动效行为类型以及定时等等，利用回调函数实现宽高自适应，因为爱心是要跳动的，大小会改变，这就要求宽高要一起变化，否则会出现特变尴尬的效果，你的爱心可能会比较抽象，，，避免此问题也很简单，直接让宽高产生联系即可，他们一起改变！

范围指定

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;
})();

大致爱心形状
简单画出大致形状，后面去进一步改进边框，让边框也实现动效，这里的关键就是爱心的凹下去的部分，可以把爱心看成是一个圆形，只是发生了一些简单的改变，凹下去一块，突出去一块。

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;
})();

边界小爱心

这个实现最为麻烦，要设置小爱心的不断更替，以及形状渐变等等，设置定时器，保证每个小爱心的出现时间有规律，这样看起来才会整齐，否则总会有点尴尬的小坚强一直不消散，还有就是要保证小爱心扩散的方向，要结合它所处的位置，如果都是直接朝着一个方向扩散会感觉很奇怪，不符合人类的直观审美，在那个位置的小爱心，就要从那个位置出发去消散，避免诙谐的感受。同时要随着大爱心的大小改变调整自己的出现位置，但是也不能全部出现在内侧，还要有一两个漏网之鱼在外面，有种凌乱美，看起来观感更佳。

var ParticlePool = (function() {var particles,firstActive = 0,firstFree   = 0,duration    = settings.particles.duration;function ParticlePool(length) {// create and populate particle poolparticles = 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 queuefirstFree++;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 particlesif (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 particleswhile (particles[firstActive].age >= duration && firstActive != firstFree) {firstActive++;if (firstActive == particles.length) firstActive = 0;}};ParticlePool.prototype.draw = function(context, image) {// draw active particlesif (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;
})();

将上述部件组装
这里就还是比较简单的啦，只需要把之前写好的部分按照预想该怎么调用就怎么调用，设置好定时器以及出现位置，因为是心形，还要结合一些数学函数，比如cos等，实现变角处理，让整个心形更加圆滑平稳，还要设置页面的显示方式，渐变出现，以及出现的速度等等。

(function(canvas) {var context = canvas.getContext('2d'),particles = new ParticlePool(settings.particles.length),particleRate = settings.particles.length / settings.particles.duration, // particles/sectime;// get point on heart with -PI <= t <= PIfunction 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);}// creating the particle image using a dummy canvasvar 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 pathfunction 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 pathcontext.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 fillcontext.fillStyle = '#ea80b0';context.fill();// create the imagevar image = new Image();image.src = canvas.toDataURL();return image;})();

边界处理以及其他设定
这里要设定好小爱心们散落的位置以及出现地址，保证跟随着大爱心一起动，同时圈定大爱心的位置。

// render that thing!function render() {// next animation framerequestAnimationFrame(render);// update timevar newTime   = new Date().getTime() / 1000,deltaTime = newTime - (time || newTime);time = newTime;// clear canvascontext.clearRect(0, 0, canvas.width, canvas.height);// create new particlesvar 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 particlesparticles.update(deltaTime);particles.draw(context, image);}// handle (re-)sizing of the canvasfunction onResize() {canvas.width  = canvas.clientWidth;canvas.height = canvas.clientHeight;}window.onresize = onResize;// delay rendering bootstrapsetTimeout(function() {onResize();render();}, 10);
})(document.getElementById('pinkboard'));

3. 完整源码

相信也有同志可能不是程序员，但被迫找到这里，这个源码只需要复制到一个空的txt文件里，然后把txt的后缀改成html打开就可以啦。

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD><TITLE> New Document </TITLE><META NAME="Generator" CONTENT="EditPlus"><META NAME="Author" CONTENT=""><META NAME="Keywords" CONTENT=""><META NAME="Description" CONTENT=""><style>html, body {height: 100%;padding: 0;margin: 0;background: #000;
}
canvas {position: absolute;width: 100%;height: 100%;
}</style></HEAD><BODY><canvas id="pinkboard"></canvas><script>/** Settings*/
var settings = {particles: {length:   500, // maximum amount of particlesduration:   2, // particle duration in secvelocity: 100, // particle velocity in pixels/seceffect: -0.75, // play with this for a nice effectsize:      30, // particle size in pixels},
};/** RequestAnimationFrame polyfill by Erik Möller*/
(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)}}}());/** Point class*/
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;
})();/** Particle class*/
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;
})();/** ParticlePool class*/
var ParticlePool = (function() {var particles,firstActive = 0,firstFree   = 0,duration    = settings.particles.duration;function ParticlePool(length) {// create and populate particle poolparticles = 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 queuefirstFree++;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 particlesif (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 particleswhile (particles[firstActive].age >= duration && firstActive != firstFree) {firstActive++;if (firstActive == particles.length) firstActive = 0;}};ParticlePool.prototype.draw = function(context, image) {// draw active particlesif (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;
})();/** Putting it all together*/
(function(canvas) {var context = canvas.getContext('2d'),particles = new ParticlePool(settings.particles.length),particleRate = settings.particles.length / settings.particles.duration, // particles/sectime;// get point on heart with -PI <= t <= PIfunction 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);}// creating the particle image using a dummy canvasvar 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 pathfunction 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 pathcontext.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 fillcontext.fillStyle = '#ea80b0';context.fill();// create the imagevar image = new Image();image.src = canvas.toDataURL();return image;})();// render that thing!function render() {// next animation framerequestAnimationFrame(render);// update timevar newTime   = new Date().getTime() / 1000,deltaTime = newTime - (time || newTime);time = newTime;// clear canvascontext.clearRect(0, 0, canvas.width, canvas.height);// create new particlesvar 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 particlesparticles.update(deltaTime);particles.draw(context, image);}// handle (re-)sizing of the canvasfunction onResize() {canvas.width  = canvas.clientWidth;canvas.height = canvas.clientHeight;}window.onresize = onResize;// delay rendering bootstrapsetTimeout(function() {onResize();render();}, 10);
})(document.getElementById('pinkboard'));</script></BODY>
</HTML>