main.js

// Settings
var settings = {
  particles: {
    length: 8000, // maximum amount of particles
    duration: 4.2, // particle duration in sec
    velocity: 80, // particle velocity in pixels/sec
    effect: -3, // play with this for a nice effect
    size: 8, // particle size in pixels
  },
};

(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) {
      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 / 100, this.y / 100);
  };

  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(0, 0);
    this.velocity = new Point(0, 0);
    this.acceleration = new Point(0, 0);
    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) * 2);
    context.globalAlpha = 1 - this.age / settings.particles.duration;
    context.drawImage(image, this.position.x - size, this.position.y - size, 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 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 = 1; 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/sec
    time;

  // get point on heart with -PI <= t <= PI
  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
    );
  }

  // creating the particle image using a dummy canvas
  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) / 600;
      point.y = settings.particles.size / 2 - (point.y * settings.particles.size) / 600;
      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 += 0.0001; // baby steps!
      point = to(t);
      context.lineTo(point.x, point.y);
    }
    context.closePath();

    // create the fill
    context.fillStyle = '#e54343';
    context.fill();

    // create the image
    var image = new Image();
    image.src = canvas.toDataURL();
    return image;
  })();

  // render that thing!
  function render() {
    // next animation frame

    requestAnimationFrame(render);

    // update time
    var newTime = new Date().getTime() / 1200,
      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 - 1000 * 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 / 2, -dir.y / 2);
    }
    // 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);
  }

  // handle (re-)sizing of the canvas
  function onResize() {
    canvas.width = canvas.clientWidth;
    canvas.height = canvas.clientHeight;
  }
  window.onresize = onResize;

  // delay rendering bootstrap
  setTimeout(function () {
    onResize();
    render();
  }, 10);
})(document.getElementById('pinkboard'));