$(function(){var currentImg = $('.main-img:first-child');var nextImg = currentImg.next();function getNextImg(img) {if($(img).prevAll().length < 4) {return $(img).next();} else {return $('.main-img:first-child');}}setInterval(function() {var oldCur = currentImg;var oldNext = nextImg;oldCur.fadeOut(1000);oldNext.fadeIn(1000);currentImg = nextImg;nextImg = getNextImg(nextImg);}, 5 * 1000);});