HTML5超炫酷粒子效果的进度条

这是一款基于HTML5和JavaScript的进度条应用，这款进度条插件非常有特点，它在进度展示的时候呈现粒子的动画效果，也就是说，进度条在滑动的同时，会产生一些小粒子掉落下来，效果非常酷。另外还有一个特点是随着进度的变化，进度条的颜色也会变化。

JavaScript代码

/*========================================================*/  
/* Light Loader
/*========================================================*/
var lightLoader = function(c, cw, ch){

    var _this = this;
    this.c = c;
    this.ctx = c.getContext('2d');
    this.cw = cw;
    this.ch = ch;            

    this.loaded = 0;
    this.loaderSpeed = .6;
    this.loaderHeight = 10;
    this.loaderWidth = 310;                
    this.loader = {
        x: (this.cw/2) - (this.loaderWidth/2),
        y: (this.ch/2) - (this.loaderHeight/2)
    };
    this.particles = [];
    this.particleLift = 180;
    this.hueStart = 0
    this.hueEnd = 120;
    this.hue = 0;
    this.gravity = .15;
    this.particleRate = 4;    

    /*========================================================*/    
    /* Initialize
    /*========================================================*/
    this.init = function(){
        this.loop();
    };

    /*========================================================*/    
    /* Utility Functions
    /*========================================================*/                
    this.rand = function(rMi, rMa){return ~~((Math.random()*(rMa-rMi+1))+rMi);};
    this.hitTest = function(x1, y1, w1, h1, x2, y2, w2, h2){return !(x1 + w1 < x2 || x2 + w2 < x1 || y1 + h1 < y2 || y2 + h2 < y1);};

    /*========================================================*/    
    /* Update Loader
    /*========================================================*/
    this.updateLoader = function(){
        if(this.loaded < 100){
            this.loaded += this.loaderSpeed;
        } else {
            this.loaded = 0;
        }
    };

    /*========================================================*/    
    /* Render Loader
    /*========================================================*/
    this.renderLoader = function(){
        this.ctx.fillStyle = '#000';
        this.ctx.fillRect(this.loader.x, this.loader.y, this.loaderWidth, this.loaderHeight);

        this.hue = this.hueStart + (this.loaded/100)*(this.hueEnd - this.hueStart);

        var newWidth = (this.loaded/100)*this.loaderWidth;
        this.ctx.fillStyle = 'hsla('+this.hue+', 100%, 40%, 1)';
        this.ctx.fillRect(this.loader.x, this.loader.y, newWidth, this.loaderHeight);

        this.ctx.fillStyle = '#222';
        this.ctx.fillRect(this.loader.x, this.loader.y, newWidth, this.loaderHeight/2);
    };    

    /*========================================================*/    
    /* Particles
    /*========================================================*/
    this.Particle = function(){                    
        this.x = _this.loader.x + ((_this.loaded/100)*_this.loaderWidth) - _this.rand(0, 1);
        this.y = _this.ch/2 + _this.rand(0,_this.loaderHeight)-_this.loaderHeight/2;
        this.vx = (_this.rand(0,4)-2)/100;
        this.vy = (_this.rand(0,_this.particleLift)-_this.particleLift*2)/100;
        this.width = _this.rand(1,4)/2;
        this.height = _this.rand(1,4)/2;
        this.hue = _this.hue;
    };

    this.Particle.prototype.update = function(i){
        this.vx += (_this.rand(0,6)-3)/100; 
        this.vy += _this.gravity;
        this.x += this.vx;
        this.y += this.vy;

        if(this.y > _this.ch){
            _this.particles.splice(i, 1);
        }                    
    };

    this.Particle.prototype.render = function(){
        _this.ctx.fillStyle = 'hsla('+this.hue+', 100%, '+_this.rand(50,70)+'%, '+_this.rand(20,100)/100+')';
        _this.ctx.fillRect(this.x, this.y, this.width, this.height);
    };

    this.createParticles = function(){
        var i = this.particleRate;
        while(i--){
            this.particles.push(new this.Particle());
        };
    };

    this.updateParticles = function(){                    
        var i = this.particles.length;                        
        while(i--){
            var p = this.particles[i];
            p.update(i);                                            
        };                        
    };

    this.renderParticles = function(){
        var i = this.particles.length;                        
        while(i--){
            var p = this.particles[i];
            p.render();                                            
        };                    
    };

    /*========================================================*/    
    /* Clear Canvas
    /*========================================================*/
    this.clearCanvas = function(){
        this.ctx.globalCompositeOperation = 'source-over';
        this.ctx.clearRect(0,0,this.cw,this.ch);                    
        this.ctx.globalCompositeOperation = 'lighter';
    };

    /*========================================================*/    
    /* Animation Loop
    /*========================================================*/
    this.loop = function(){
        var loopIt = function(){
            requestAnimationFrame(loopIt, _this.c);
            _this.clearCanvas();

            _this.createParticles();

            _this.updateLoader();
            _this.updateParticles();

            _this.renderLoader();
            _this.renderParticles();

        };
        loopIt();                    
    };

};

/*========================================================*/    
/* Check Canvas Support
/*========================================================*/
var isCanvasSupported = function(){
    var elem = document.createElement('canvas');
    return !!(elem.getContext && elem.getContext('2d'));
};

/*========================================================*/    
/* Setup requestAnimationFrame
/*========================================================*/
var setupRAF = function(){
    var lastTime = 0;
    var vendors = ['ms', 'moz', 'webkit', 'o'];
    for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x){
        window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame'];
        window.cancelAnimationFrame = window[vendors[x]+'CancelAnimationFrame'] || window[vendors[x]+'CancelRequestAnimationFrame'];
    };

    if(!window.requestAnimationFrame){
        window.requestAnimationFrame = function(callback, element){
            var currTime = new Date().getTime();
            var timeToCall = Math.max(0, 16 - (currTime - lastTime));
            var id = window.setTimeout(function() { callback(currTime + timeToCall); }, timeToCall);
            lastTime = currTime + timeToCall;
            return id;
        };
    };

    if (!window.cancelAnimationFrame){
        window.cancelAnimationFrame = function(id){
            clearTimeout(id);
        };
    };
};            

/*========================================================*/    
/* Define Canvas and Initialize
/*========================================================*/
if(isCanvasSupported){
  var c = document.createElement('canvas');
  c.width = 400;
  c.height = 100;            
  var cw = c.width;
  var ch = c.height;    
  document.body.appendChild(c);    
  var cl = new lightLoader(c, cw, ch);                

  setupRAF();
  cl.init();
}
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