Jquery to achieve the image page turning effect

$(function($){
    $.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;
}