年底为了体现过年的气氛，很多网页会做各种喜气的特效，现在我们来学习一下jquery网页下雪特效插件，这样你的网页也可以有冬天的年味了。 又到了年底，从圣诞节开始，可以发现各大网站的活动是越来越...

年底为了体现过年的气氛，很多网页会做各种喜气的特效，现在我们来学习一下jquery网页下雪特效插件，这样你的网页也可以有冬天的年味了。

又到了年底，从圣诞节开始，可以发现各大网站的活动是越来越多，都变的银装素裹，本人由于业务需求也需要做这么一个效果，所以就通过google大神找了一下相关资源，结果就出现了N种雪花效果的方式。种类繁多，最后找到了本文看到的这种效果，原作者写的可以说已经满足了我的需求，但是为了符合更多的场景，又再原作者的基础上做了调整。
 
声明：本文核心代码归原作者@Ivan Lazarevic（https://github.com/kopipejst）所有，本人只增加了一些参数和效果

兼容性：除IE外各主流浏览器（当然也可以调整代码，支持IE高版本浏览器，本文实例不支持IE）

经过调整的代码如下：
（上半部分为jquery-easing，下半部分为雪花效果）

 代码如下 复制代码

(function($){
    /*
 * jQuery Easing v1.3 -
 *
 * Uses the built in easing capabilities added In jQuery 1.1
 * to offer multiple easing options
 *
 * TERMS OF USE - jQuery Easing
 *
 * Open source under the BSD License.
 *
 * Copyright © 2008 George McGinley Smith
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this list of
 * conditions and the following disclaimer.
 * Redistributions in binary form must reproduce the above copyright notice, this list
 * of conditions and the following disclaimer in the documentation and/or other materials
 * provided with the distribution.
 *
 * Neither the name of the author nor the names of contributors may be used to endorse
 * or promote products derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 *  COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 *  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 *  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
*/
 
// t: current time, b: begInnIng value, c: change In value, d: duration
jQuery.easing['jswing'] = jQuery.easing['swing'];
 
jQuery.extend( jQuery.easing,
{
    def: 'easeOutQuad',
    swing: function (x, t, b, c, d) {
        //alert(jQuery.easing.default);
        return jQuery.easing[jQuery.easing.def](x, t, b, c, d);
    },
    easeInQuad: function (x, t, b, c, d) {
        return c*(t/=d)*t + b;
    },
    easeOutQuad: function (x, t, b, c, d) {
        return -c *(t/=d)*(t-2) + b;
    },
    easeInOutQuad: function (x, t, b, c, d) {
        if ((t/=d/2) < 1) return c/2*t*t + b;
        return -c/2 * ((--t)*(t-2) - 1) + b;
    },
    easeInCubic: function (x, t, b, c, d) {
        return c*(t/=d)*t*t + b;
    },
    easeOutCubic: function (x, t, b, c, d) {
        return c*((t=t/d-1)*t*t + 1) + b;
    },
    easeInOutCubic: function (x, t, b, c, d) {
        if ((t/=d/2) < 1) return c/2*t*t*t + b;
        return c/2*((t-=2)*t*t + 2) + b;
    },
    easeInQuart: function (x, t, b, c, d) {
        return c*(t/=d)*t*t*t + b;
    },
    easeOutQuart: function (x, t, b, c, d) {
        return -c * ((t=t/d-1)*t*t*t - 1) + b;
    },
    easeInOutQuart: function (x, t, b, c, d) {
        if ((t/=d/2) < 1) return c/2*t*t*t*t + b;
        return -c/2 * ((t-=2)*t*t*t - 2) + b;
    },
    easeInQuint: function (x, t, b, c, d) {
        return c*(t/=d)*t*t*t*t + b;
    },
    easeOutQuint: function (x, t, b, c, d) {
        return c*((t=t/d-1)*t*t*t*t + 1) + b;
    },
    easeInOutQuint: function (x, t, b, c, d) {
        if ((t/=d/2) < 1) return c/2*t*t*t*t*t + b;
        return c/2*((t-=2)*t*t*t*t + 2) + b;
    },
    easeInSine: function (x, t, b, c, d) {
        return -c * Math.cos(t/d * (Math.PI/2)) + c + b;
    },
    easeOutSine: function (x, t, b, c, d) {
        return c * Math.sin(t/d * (Math.PI/2)) + b;
    },
    easeInOutSine: function (x, t, b, c, d) {
        return -c/2 * (Math.cos(Math.PI*t/d) - 1) + b;
    },
    easeInExpo: function (x, t, b, c, d) {
        return (t==0) ? b : c * Math.pow(2, 10 * (t/d - 1)) + b;
    },
    easeOutExpo: function (x, t, b, c, d) {
        return (t==d) ? b+c : c * (-Math.pow(2, -10 * t/d) + 1) + b;
    },
    easeInOutExpo: function (x, t, b, c, d) {
        if (t==0) return b;
        if (t==d) return b+c;
        if ((t/=d/2) < 1) return c/2 * Math.pow(2, 10 * (t - 1)) + b;
        return c/2 * (-Math.pow(2, -10 * --t) + 2) + b;
    },
    easeInCirc: function (x, t, b, c, d) {
        return -c * (Math.sqrt(1 - (t/=d)*t) - 1) + b;
    },
    easeOutCirc: function (x, t, b, c, d) {
        return c * Math.sqrt(1 - (t=t/d-1)*t) + b;
    },
    easeInOutCirc: function (x, t, b, c, d) {
        if ((t/=d/2) < 1) return -c/2 * (Math.sqrt(1 - t*t) - 1) + b;
        return c/2 * (Math.sqrt(1 - (t-=2)*t) + 1) + b;
    },
    easeInElastic: function (x, t, b, c, d) {
        var s=1.70158;var p=0;var a=c;
        if (t==0) return b;  if ((t/=d)==1) return b+c;  if (!p) p=d*.3;
        if (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;
    },
    easeOutElastic: function (x, t, b, c, d) {
        var s=1.70158;var p=0;var a=c;
        if (t==0) return b;  if ((t/=d)==1) return b+c;  if (!p) p=d*.3;
        if (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;
    },
    easeInOutElastic: function (x, t, b, c, d) {
        var s=1.70158;var p=0;var a=c;
        if (t==0) return b;  if ((t/=d/2)==2) return b+c;  if (!p) p=d*(.3*1.5);
        if (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 -.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 )*.5 + c + b;
    },
    easeInBack: function (x, t, b, c, d, s) {
        if (s == undefined) s = 1.70158;
        return c*(t/=d)*t*((s+1)*t - s) + b;
    },
    easeOutBack: function (x, t, b, c, d, s) {
        if (s == undefined) s = 1.70158;
        return c*((t=t/d-1)*t*((s+1)*t + s) + 1) + b;
    },
    easeInOutBack: function (x, t, b, c, d, s) {
        if (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;
    },
    easeInBounce: function (x, t, b, c, d) {
        return c - jQuery.easing.easeOutBounce (x, d-t, 0, c, d) + b;
    },
    easeOutBounce: function (x, 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 + .75) + b;
        } else if (t < (2.5/2.75)) {
            return c*(7.5625*(t-=(2.25/2.75))*t + .9375) + b;
        } else {
            return c*(7.5625*(t-=(2.625/2.75))*t + .984375) + b;
        }
    },
    easeInOutBounce: function (x, t, b, c, d) {
        if (t < d/2) return jQuery.easing.easeInBounce (x, t*2, 0, c, d) * .5 + b;
        return jQuery.easing.easeOutBounce (x, t*2-d, 0, c, d) * .5 + c*.5 + b;
    }
});
 
/*
 *
 * TERMS OF USE - EASING EQUATIONS
 *
 * Open source under the BSD License.
 *
 * Copyright © 2001 Robert Penner
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this list of
 * conditions and the following disclaimer.
 * Redistributions in binary form must reproduce the above copyright notice, this list
 * of conditions and the following disclaimer in the documentation and/or other materials
 * provided with the distribution.
 *
 * Neither the name of the author nor the names of contributors may be used to endorse
 * or promote products derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 *  COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 *  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 *  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
 
 
    $.fn.snow = function(options){
        //处理浏览器
        var na = window.navigator;
        var ua = na.userAgent.toLowerCase();
        var browserTester = /(webkit|gecko|presto|opera|safari|firefox|chrome|applewebkit)[ /os]*([d_.]+)/ig
        if(!browserTester.test(ua)) {
            return;
        }
        
        var winHeight = $(window).height();
        var docHeight = $(document).height();
        var docWidth = $(document).width();
        var defaults = {
            minSize: 20,        //雪花的最小尺寸
            maxSize: 50,        //雪花的最大尺寸
            speed: docHeight * 10, //雪花掉落速度
            frequency: 500,     //雪花出现的频率
            color: "#FFFFFF", //雪花颜色
            easing: 'linear', //雪花动画效果
            position: 'absolute' //定位方式
        };
        var options = $.extend({}, defaults, options);
        var $snow = $('<div>').css({'position': options.position, 'top': '-50px', 'z-index':9999999999}).html('❄');
        var height = options.position == "fixed" ? winHeight : docHeight;
        var width = docWidth;
        
        $('body').css('overflow-x', 'hidden');
        
        var interval = setInterval( function(){
            var startPositionLeft = Math.random() * width - 100;
            var startOpacity = 0.5 + Math.random();
            var size = options.minSize + Math.random() * options.maxSize;
            var endPositionTop = height - 40;
            var endPositionLeft = startPositionLeft + (Math.random()*10 > 5 ? -500 : 500);
 
            $snow.clone().appendTo('body').css({
                        left: startPositionLeft,
                        opacity: startOpacity,
                        'font-size': size,
                        color: options.color
                    }).animate({
                        top: endPositionTop,
                        left: endPositionLeft,
                        opacity: 0.2
                    },options.speed, options.easing,function(){
                        $(this).remove()
                    }
                );
                
        }, options.frequency);
    
    };
    
})(jQuery);