$(function($){     $.fn.changeList = function(options){         var defaults = {                     tag : 'li', // tab name                     subName : '.utilTabSub', // sub class name                     eventType : 'click', // event type                     num : 4,                     showType : 'show' // show effect type                 },                 opts = $.extend({}, defaults, options),                 that = $(this),                 subUl = that.find(opts.subName),                 subItems = subUl.find('li'),                 size = subItems.length,                 liW = subItems.outerWidth(true),                 ulW = liW * size,                 page = size + 1,                 n = opts.num,                 randNum = 0,                 m = 0;           if(size > n){             that.find(opts.tag)[opts.eventType](function() {                 randNum = mathRand(n, size);                 subItems.hide();                 $.each(randNum, function (i, el) {                     subItems.eq(el).fadeIn(800);                 });             });         }     }; }(jQuery));   /**  * create Random number  * @param bit: number  * @param max: max number  * @return {Array}  */ function mathRand(bit, max){     var num = 0,             arr = [],             ret = [];     for(var i=0; i<bit; i++){         num = Math.floor(Math.random() * max);         if($.inArray(num, ret) == -1){             ret.push(num);         } else {             i--;             continue;         }     }     return ret; }