// javascript
var gallery = document.getElementById("gallery");
var previous = document.getElementById("previous");
var next = document.getElementById("next");
var item = 0;

next.addEventListener('click', nextItem);
previous.addEventListener('click', previousItem);

function nextItem() {
    if (item < 4) {
        item++;  
    }   
    else if (item >=4 ) {
        item = 0
    }      
    changeItem();
}

function previousItem() {
    if (item > 0) {
        item--; 
    }
    else if (item <= 0) {
        item = 4;
    }          
    changeItem();
}

function changeItem() {    
    switch(item) {
        case 0: gallery.style.transform = "translateX(0px)";
        break;
        case 1: gallery.style.transform = "translateX(-220px)";
        break;
        case 2: gallery.style.transform = "translateX(-440px)";
        break;
        case 3: gallery.style.transform = "translateX(-660px)";
        break;
        case 4: gallery.style.transform = "translateX(-880px)";
        break;
            }

}