面向对象产生随机萤火虫效果

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title>随机萤火虫</title>
        <style type="text/css">
            *{
                margin: 0;
                padding: 0;
            }
            body,html{
                height: 100%;
                width: 100%;
            }
            #bg{
                width: 100%;
                height: 100%;
                background: url(img/bg.jpg) no-repeat;
                background-size: cover;
            }
            img{
                display: block;
                position: absolute;
                top: 0;
                left: 0;
            }
        </style>
    </head>
    <body>
        <script src="js/Tween.js" type="text/javascript" charset="utf-8"></script>
        <div id="bg"></div>
        <script type="text/javascript">
            //构造函数
            function Firefly(){
                this.oBg = document.getElementById("bg");
                this.oImg = document.createElement('img');
            }
            //给新创建的萤火虫设置大小、位置
            Firefly.prototype.occur = function(){
                this.oImg.src = 'img/star.jpg';
                this.oImg.style.width = this.oWidth + 'px';
                this.oImg.style.height = this.oWidth + 'px';
                this.oImg.style.top = this.oTop + 'px';
                this.oImg.style.left = this.oLeft + 'px';
                this.oBg.appendChild( this.oImg );
                return this;
            }
            //获取萤火虫的随机位置、大小
            Firefly.prototype.randomPlace = function(){
                this.oLeft = this.randomNUm( window.innerWidth - 50 );
                this.oTop = this.randomNUm( window.innerHeight - 50 );
                this.oWidth = this.randomNUm(20) + 12;
                return this;
            }
            //飞行时间控制在5-10秒
            Firefly.prototype.flyTime = function(){    
                this.oTime = Math.floor( Math.random() * 5 + 5 ) * 1000;
                return this;
            }
            //调用运动函数使萤火虫飞行
            Firefly.prototype.fly = function(){
                var This = this;
                this.oImg.sport( This.oImg , {'top':this.oTop,'left':this.oLeft} , this.oTime ,function(){
                    This.flyTime().occur().randomPlace().fly();
                } );
            }
            //构造一个范围内的随机数
            Firefly.prototype.randomNUm = function( num ){   
                return Math.floor( Math.random()*num );
            }
            var fireFly = [];
            for( var i = 0;i<50;i++ )
            {
                //构造50个萤火虫
                fireFly[i] = new Firefly();             
                fireFly[i].randomPlace().flyTime().occur().randomPlace().fly();
            }
        </script>
    </body>
</html>

//Tween.js代码
Object.prototype.sport = function( obj , Json , time , ev , fn ){
    if ( typeof ev == 'undefined' )
    {
        time = time || 400;
        ev = 'linear';
    }
    if ( typeof time == 'string' )
    {
        fn = ev;
        ev = time;
        time = 400;
    }else if ( typeof time == 'number' && typeof ev == 'function' )
    {
        fn = ev;
        ev = 'linear';
    }else if ( typeof time == 'function' )
    {
        fn = time;
        time = 400;
        ev = 'linear';
    }
    var This = this;
    var oB = {};
    for( attr in Json )
    {
        oB[attr] = parseInt( this.getStyle( this , attr ) );
    }
    var oC = {};
    for( attr in Json )
    {
        oC[attr] = Json[attr];
    }
    var startTime = new Date().getTime();
    clearInterval( this.timer );
    obj.timer = setInterval( function(){
        var nowTime = new Date().getTime();
        var time2 = Math.min(nowTime - startTime , time);
        for( attr in Json )    //t,b,c,d
        {
            var oChange = Tween[ev]( time2 , oB[attr] , oC[attr] - oB[attr] , time );
            if( attr == 'opacity' )
            {
                obj.style[attr] = oChange;
                obj.style.filter = 'alpha(opacity='+(oChange*100)+')';
            }else{
                obj.style[attr] = oChange + 'px';
            }
            
        }
        if( time2 == time )
        {
            clearInterval( obj.timer );
            fn && fn( This );
        }
    } ,30 );
}
Object.prototype.getStyle = function( obj , att ){
    return obj.currentStyle ? obj.currentStyle[att] : getComputedStyle( obj )[att];
}
var Tween = {
    linear: function (t, b, c, d){  //匀速
        return c*t/d + b;
    },
    easeIn: function(t, b, c, d){  //加速曲线
        return c*(t/=d)*t + b;
    },
    easeOut: function(t, b, c, d){  //减速曲线
        return -c *(t/=d)*(t-2) + b;
    },
    easeBoth: function(t, b, c, d){  //加速减速曲线
        if ((t/=d/2) <   1) {
            return c/2*t*t + b;
        }
        return -c/2 * ((--t)*(t-2) - 1) + b;
    },
    easeInStrong: function(t, b, c, d){  //加加速曲线
        return c*(t/=d)*t*t*t + b;
    },
    easeOutStrong: function(t, b, c, d){  //减减速曲线
        return -c * ((t=t/d-1)*t*t*t - 1) + b;
    },
    easeBothStrong: function(t, b, c, d){  //加加速减减速曲线
        if ((t/=d/2) < 1) {
            return c/2*t*t*t*t + b;
        }
        return -c/2 * ((t-=  2)*t*t*t - 2) + b;
    },
    elasticIn: function(t, b, c, d, a, p){  //正弦衰减曲线（弹动渐入）
        if (t === 0) { 
            return b; 
        }
        if ( (t /= d) == 1 ) {
            return b+c; 
        }
        if (!p) {
            p=d*0.3; 
        }
        if (!a || a < Math.abs(c)) {
            a = c; 
            var s = p/4;
        } else {
            var s = p/(2*Math.PI) * Math.asin (c/a);
        }
        return -(a*Math.pow(2,10*(t-=  1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
    },
    elasticOut: function(t, b, c, d, a, p){    //正弦增强曲线（弹动渐出）
        if (t === 0) {
            return b;
        }
        if ( (t /= d) == 1 ) {
            return b+c;
        }
        if (!p) {
            p=d*0.3;
        }
        if (!a || a < Math.abs(c)) {
            a = c;
            var s = p / 4;
        } else {
            var s = p/(2*Math.PI) * Math.asin (c/a);
        }
        return a*Math.pow(2,-10*t) * Math.sin( (t*d-s)*(2*Math.PI)/p ) + c + b;
    },    
    elasticBoth: function(t, b, c, d, a, p){
        if (t === 0) {
            return b;
        }
        if ( (t /= d/2) == 2 ) {
            return b+c;
        }
        if (!p) {
            p = d*(0.3*1.5);
        }
        if ( !a || a < Math.abs(c) ) {
            a = c; 
            var s = p/4;
        }
        else {
            var s = p/(2*Math.PI) * Math.asin (c/a);
        }
        if (t < 1) {
            return - 0.5*(a*Math.pow(2,10*(t-=  1)) * 
                    Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
        }
        return a*Math.pow(2,-10*(t-=  1)) * 
                Math.sin( (t*d-s)*(2*Math.PI)/p )*0.5 + c + b;
    },
    backIn: function(t, b, c, d, s){     //回退加速（回退渐入）
        if (typeof s == 'undefined') {
           s =   1.70158;
        }
        return c*(t/=d)*t*((s+1)*t - s) + b;
    },
    backOut: function(t, b, c, d, s){
        if (typeof s == 'undefined') {
            s =   3.70158;  //回缩的距离
        }
        return c*((t=t/d-1)*t*((s+1)*t + s) + 1) + b;
    }, 
    backBoth: function(t, b, c, d, s){
        if (typeof s == 'undefined') {
            s =   1.70158; 
        }
        if ((t /= d/2 ) < 1) {
            return c/2*(t*t*(((s*=(1.525))+1)*t - s)) + b;
        }
        return c/2*((t-=  2)*t*(((s*=(1.525))+1)*t + s) + 2) + b;
    },
    bounceIn: function(t, b, c, d){    //弹球减振（弹球渐出）
        return c - Tween['bounceOut'](d-t, 0, c, d) + b;
    },       
    bounceOut: function(t, b, c, d){
        if ((t/=d) < (1/2.75)) {
            return c*(7.5625*t*t) + b;
        } else if (t < (2/2.75)) {
            return c*(7.5625*(t-=(1.5/2.75))*t + 0.75) + b;
        } else if (t < (2.5/2.75)) {
            return c*(7.5625*(t-=(2.25/2.75))*t + 0.9375) + b;
        }
        return c*(7.5625*(t-=(2.625/2.75))*t + 0.984375) + b;
    },      
    bounceBoth: function(t, b, c, d){
        if (t < d/2) {
            return Tween['bounceIn'](t*2, 0, c, d) * 0.5 + b;
        }
        return Tween['bounceOut'](t*2-d, 0, c, d) * 0.5 + c*0.5 + b;
    }
}



 






        

	      

	    

	  

	  

	    
      
        【推广】
        免费学中医，健康全家人
      
	  

    

    

          原文地址：https://www.cnblogs.com/lijiahui199494/p/5855200.html