var currentSlide = 0; var allSlides = document.querySelectorAll(".programGallery"); window.nextSlide = function nextSlide(){ currentSlide++; updateSlide(); } window.lastSlide = function lastSlide(){ currentSlide--; updateSlide(); } function updateSlide(){ if (currentSlide > allSlides.length-1){ currentSlide = 0; } else if (currentSlide < 0){ currentSlide = allSlides.length-1; } hideAll(); allSlides[currentSlide].style.display = "grid"; } function hideAll(){ for (var i = 0; i < allSlides.length; i++){ allSlides[i].style.display = "none"; } } hideAll() updateSlide();