网页的雪花飘落效果

前几天再编辑自己的网页时想到上次百度做炸鸡啤酒那个雪花飘落，于是有兴趣就在网络上找了一找，找到了没有凝视的源代码，于是自己就学习了一下，而且为代码加入上凝视和大家分享，源代码地址也已经贴出。凝视不知道是否正确，有问题大家能够留言。

js部分

(function(){
    function k(a, b, c) {
        if (a.addEventListener) a.addEventListener(b, c, false);
        else a.attachEvent && a.attachEvent("on" + b, c)
    }//加入监听事件函数
    function g(a) {
        if (typeof window.onload != "function") window.onload = a;
        else {
            var b = window.onload;
            window.onload = function() {
                b();
                a()
            }
        }
    }//页面载入时就能够进行绘制
    function h() {
        var a = {};
        for (type in {
            Top: "",
            Left: ""
        }) {
            var b = type == "Top" ? "Y": "X";
            if (typeof window["page" + b + "Offset"] != "undefined") a[type.toLowerCase()] = window["page" + b + "Offset"];
            else {
                b = document.documentElement.clientHeight ? document.documentElement: document.body;
                a[type.toLowerCase()] = b["scroll" + type]
            }
        }
        return a
    }//top为向下已经拖动的高度，left为向左已经拖动的宽度
    function l() {
        var a = document.body,
        b;
        if (window.innerHeight) b = window.innerHeight;
        else if (a.parentElement.clientHeight) b = a.parentElement.clientHeight;
        else if (a && a.clientHeight) b = a.clientHeight;
        return b
    }//获取当前屏幕网页宽度
    function i(a) {
        this.parent = document.body;
        this.createEl(this.parent, a);
        this.size = Math.random() * 5 + 5;
        this.el.style.width = Math.round(this.size) + "px";
        this.el.style.height = Math.round(this.size) + "px";//img节点大小
        this.maxLeft = document.body.offsetWidth - this.size;//左边界
        this.maxTop = document.body.offsetHeight - this.size;//下边界
        this.left = Math.random() * this.maxLeft;//初始X轴
        this.top = h().top + 1;//初始Y轴
        this.angle = 1.4 + 0.2 * Math.random();//初始角度
        this.minAngle = 1.4;//摆动角度范围1.4pi~1.6pi
        this.maxAngle = 1.6;
        this.angleDelta = 0.01 * Math.random();//角度变动
        this.speed = 2 + Math.random()//移动速度，2~3不等
    }
    var j = false;
    g(function() {
        j = true
    });
    var f = true;
    window.createSnow = function(a, b) {
        if (j) {
            var c = [],
            m = setInterval(function() {
                f && b > c.length && Math.random() < b * 0.0025 && c.push(new i(a)); //限定雪花数组大小
				! f && !c.length && clearInterval(m);//条件符合，清除雪花
                for (var e = h().top, n = l(), d = c.length - 1; d >= 0; d--) if (c[d]) if (c[d].top < e || c[d].top + c[d].size + 1 > e + n) {
                    c[d].remove();
                    c[d] = null;
                    c.splice(d, 1)//雪花超出底线，删除
                } else {
                    c[d].move();//雪花移动
                    c[d].draw()//雪花绘制
                }
            },
            40);//40ms一跳
            k(window, "scroll",
            function() {
                for (var e = c.length - 1; e >= 0; e--) c[e].draw()
            })//监听滚动栏时间，滚动重绘
        } else g(function() {
            createSnow(a, b)
        })
    };
    window.removeSnow = function() {
        f = false
    };//移除雪花绘制
    i.prototype = {
        createEl: function(a, b) {
            this.el = document.createElement("img"); 	//加入img节点
            this.el.setAttribute("src", b + "snow" + Math.floor(Math.random() * 4) + ".gif");  	//设置雪花图片路径，种类为snow0~3随机
            this.el.style.position = "absolute";	//绝对的布局显示
            this.el.style.display = "block";	//将雪花定义为块级元素
            this.el.style.zIndex = "99999";	//在最前方显示
            this.parent.appendChild(this.el)	//加入节点
        },
        move: function() {
            if (this.angle < this.minAngle || this.angle > this.maxAngle) this.angleDelta = -this.angleDelta;//保证角度在1.4到1.6之间
            this.angle += this.angleDelta;//角度变换
            this.left += this.speed * Math.cos(this.angle * Math.PI);//x轴位移计算
            this.top -= this.speed * Math.sin(this.angle * Math.PI);//Y轴位移计算
            if (this.left < 0) this.left = this.maxLeft;	//边界判定，雪花过边界重还有一边界穿出
            else if (this.left > this.maxLeft) this.left = 0
        },
        draw: function() {
            this.el.style.top = Math.round(this.top) + "px";//定义纵轴位置
            this.el.style.left = Math.round(this.left) + "px"//定义横轴位置
        },
        remove: function() {
            this.parent.removeChild(this.el);//移除雪花元素
            this.parent = this.el = null
        }
    }
})();

在网页中加入：

<script src="jsized.snow.min.js" type="text/javascript"></script>        
<script>
    /**
     * This function takes 2 arguments
     * First is the path to the directory with snowflake images
     * Second is the maximum number of snowflakes, please do not
     * set this number above 60 as it will impact the performance
     */
    createSnow('', 60);
</script>

效果站点：http://hhteam.duapp.com/

雪花图片已经贴出，右击另存为就可以

源代码下载地址在回复中贴出