<script>(function ($) { $.fn.snow = function (options) { var $flake = $(‘<div id="flake" />‘).css({ ‘position‘: ‘absolute‘, ‘top‘: ‘-50px‘ }).html(‘❄‘), documentHeight = $(document).height(), documentWidth = $(document).width(), defaults = { minSize: 10, maxSize: 20, newOn: 500, flakeColor: "#FFFFFF" }, options = $.extend({}, defaults, options); var interval = setInterval(function () { var startPositionLeft = Math.random() * documentWidth - 100, startOpacity = 0.5 + Math.random(), sizeFlake = options.minSize + Math.random() * options.maxSize, endPositionTop = documentHeight - 40, endPositionLeft = startPositionLeft - 100 + Math.random() * 200, durationFall = documentHeight * 10 + Math.random() * 5000; $flake.clone().appendTo(‘body‘).css({ left: startPositionLeft, opacity: startOpacity, ‘font-size‘: sizeFlake, color: options.flakeColor }).animate({ top: endPositionTop, left: endPositionLeft, opacity: 0.2 }, durationFall, ‘linear‘, function () { $(this).remove() }); }, options.newOn); }; })(jQuery);<script>
原文：http://www.cnblogs.com/lbczzvv/p/7660474.html