HTML5超炫酷粒子效果的进度条的实现示例

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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