(function () {
     var count;

     function setRandomImage() {
         var number = Math.floor(Math.random() * 100) + 1;
         
         var link = document.getElementById("recommend_link");
         link.setAttribute("href", "./itiosi/recommend" + number + ".html");
         var img = document.getElementById("recommend_image");
         img.setAttribute("src", imgArray[number - 1]);

         count = number;
     }
     
     function changeImageFunc(val) {
         return function () {
             count = count + val;

             if (count >= 101) {
                 count = 1;
             } else if (count < 0) {
                 count = 100;
             }

             var link = document.getElementById("recommend_link");
             var nextHref = "./itiosi/recommend" + count + ".html";
             link.setAttribute("href", nextHref);

             var img = document.getElementById("recommend_image");
             img.setAttribute("src", imgArray[count - 1]);
         };
     }

     window.onload = function () {
         var prevButton = document.getElementById("previousButton");
         var nextButton = document.getElementById("nextButton");

         setRandomImage();

         prevButton.onclick = changeImageFunc(-1);
         nextButton.onclick = changeImageFunc(1);
     };
 })();