HTML5超炫酷粒子效果的进度条的实现示例

/*========================================================*/  /* 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();}