Arkadaşlar herkese selam, sitede kullanmış olduğum sliderda next - prev butonları çalışmıyor bir yerlerde gözümden kaçan bir şey var bir destek atabilir misiniz?

html;

<!-- Slideshow Container Start -->

<div class="slider">


<div class="list">

<div class="item">
<img src="assets/images/slider/522940_shutterstock_1073661338_384074.jpg" alt="">

<div class="content">
<div class="title">Mikrobiyolojik</div>
<div class="type">Gıda Analizleri</div>

<div class="button">
<a href=>
<button>Daha Fazlası İçin</button>
</a>
</div>
</div>
</div>

<div class="item">
<img src="assets/images/slider/522940_shutterstock_1073661338_384074.jpg" alt="">

<div class="content">
<div class="title">Mikrobiyolojik</div>
<div class="type">Su Analizleri</div>

<div class="button">
<a href=>
<button>Daha Fazlası İçin</button>
</a>
</div>
</div>
</div>

<div class="item">
<img src="assets/images/slider/522940_shutterstock_1073661338_384074.jpg" alt="">

<div class="content">
<div class="title">Fiziksel ve Kimyasal</div>
<div class="type">Su Analizleri</div>
<div class="button">
<a href=>
<button>Daha Fazlası İçin</button>
</a>
</div>
</div>
</div>

<div class="item">
<img src="assets/images/slider/522940_shutterstock_1073661338_384074.jpg" alt="">

<div class="content">
<div class="title">Hijyen</div>
<div class="type">Analizleri</div>

<div class="button">
<a href=>
<button>Daha Fazlası İçin</button>
</a>
</div>
</div>
</div>

</div>


<div class="thumbnail">

<div class="item">
<img src="assets/images/slider/522940_shutterstock_1073661338_384074.jpg" alt="">
</div>
<div class="item">
<img src="assets/images/slider/522940_shutterstock_1073661338_384074.jpg" alt="">
</div>
<div class="item">
<img src="assets/images/slider/522940_shutterstock_1073661338_384074.jpg" alt="">
</div>
<div class="item">
<img src="assets/images/slider/522940_shutterstock_1073661338_384074.jpg" alt="">
</div>

</div>


<div class="nextPrevArrows">
<button class="prev"> < </button>
<button class="next"> > </button>
</div>


</div>

<!-- Slideshow Container End-->


JS;

let nextBtn = document.querySelector('.next');
let prevBtn = document.querySelector('.prev');

let slider = document.querySelector('.slider');
let sliderList = slider.querySelector('.list');
let thumbnail = document.querySelector('.thumbnail');
let thumbnailItems = thumbnail.querySelectorAll('.item');

// İlk öğeyi thumbnail'a taşıyoruz
thumbnail.appendChild(thumbnailItems[0]);

nextBtn.onclick = function() {
moveSlider('next');
}

// Prev butonuna tıklama işlevi
prevBtn.onclick = function() {
moveSlider('prev');
}


function moveSlider(direction) {
let sliderItems = sliderList.querySelectorAll('.item');
let thumbnailItems = thumbnail.querySelectorAll('.item');

if (direction === 'next') {
// İlk öğeyi sona taşıyoruz
sliderList.appendChild(sliderItems[0]);
thumbnail.appendChild(thumbnailItems[0]);
slider.classList.add('next');
} else {
// Son öğeyi başa taşıyoruz
sliderList.prepend(sliderItems[sliderItems.length - 1]);
thumbnail.prepend(thumbnailItems[thumbnailItems.length - 1]);
slider.classList.add('prev');
}

// Animasyon sonlandığında sınıfları kaldırıyoruz
slider.addEventListener('animationend', function() {
slider.classList.remove(direction === 'next' ? 'next' : 'prev');
}, { once: true }); // Event listener sadece bir kez çalışacak
}

CSS;


.slider{
height: 100vh;
margin-top: -50px;
width: 100vw;
overflow: hidden;
position: relative;
}
.slider .list .item{
width: 100%;
height: 100%;
position: absolute;
inset: 0 0 0 0;
}
.slider .list .item img{
width: 100%;
height: 100%;
object-fit: cover;
}
.slider .list .item .content{
position: absolute;
top: 20%;
width: 1140px;
max-width: 80%;
left: 50%;
transform: translateX(-50%);
padding-right: 30%;
box-sizing: border-box;
color: #fff;
text-shadow: 0 5px 10px #0004;
}

.slider .list .item .content .title,
.slider .list .item .content .type{
font-size: 5em;
font-weight: bold;
line-height: 1.3em;
}
.slider .list .item .type{
color: #14ff72cb;
}
.slider .list .item .button{
display: grid;
grid-template-columns: repeat(2, 130px);
grid-template-rows: 40px;
gap: 5px;
margin-top: 20px;
}
.slider .list .item .button button{
border: none;
background-color: #eee;
font-family: Poppins;
font-weight: 500;
cursor: pointer;
transition: 0.4s;
letter-spacing: 2px;
}


.slider .list .item .button button:hover{
letter-spacing: 3px;
}
.slider .list .item .button button:nth-child(2){
background-color: transparent;
border: 1px solid #fff;
color: #eee;
}





/* Thumbnail Section */
.thumbnail{
position: absolute;
bottom: 50px;
left: 50%;
width: max-content;
z-index: 100;
display: flex;
gap: 20px;
}

.thumbnail .item{
width: 150px;
height: 220px;
flex-shrink: 0;
position: relative;
}

.thumbnail .item img{
width: 100%;
height: 100%;
object-fit: cover;
border-radius: 20px;
box-shadow: 5px 0 15px rgba(0, 0, 0, 0.3);
}


/* nextPrevArrows Section */
.nextPrevArrows{
position: absolute;
top: 80%;
right: 52%;
z-index: 100;
width: 300px;
max-width: 30%;
display: flex;
gap: 10px;
align-items: center;
}
.nextPrevArrows button{
width: 40px;
height: 40px;
border-radius: 50%;
background-color: #14ff72cb;
border: none;
color: #fff;
font-family: monospace;
font-weight: bold;
transition: .5s;
cursor: pointer;
}
.nextPrevArrows button:hover{
background-color: #fff;
color: #000;
}

/* Animation Part */
.slider .list .item:nth-child(1){
z-index: 1;
}


/* animation text in first item */
.slider .list .item:nth-child(1) .content .title,
.slider .list .item:nth-child(1) .content .type,
.slider .list .item:nth-child(1) .content .description,
.slider .list .item:nth-child(1) .content .buttons
{
transform: translateY(50px);
filter: blur(20px);
opacity: 0;
animation: showContent .5s 1s linear 1 forwards;
}
@keyframes showContent{
to{
transform: translateY(0px);
filter: blur(0px);
opacity: 1;
}
}
.slider .list .item:nth-child(1) .content .title{
animation-delay: 0.4s !important;
}
.slider .list .item:nth-child(1) .content .type{
animation-delay: 0.6s !important;
}
.slider .list .item:nth-child(1) .content .description{
animation-delay: 0.8s !important;
}
.slider .list .item:nth-child(1) .content .buttons{
animation-delay: 1s !important;
}




/* Animation for next button click */
.slider.next .list .item:nth-child(1) img{
width: 150px;
height: 220px;
position: absolute;
bottom: 50px;
left: 50%;
border-radius: 30px;
animation: showImage .5s linear 1 forwards;
}

@keyframes showImage{
to{
bottom: 0;
left: 0;
width: 100%;
height: 100%;
border-radius: 0;
}
}

.slider.next .thumbnail .item:nth-last-child(1){
overflow: hidden;
animation: showThumbnail .5s linear 1 forwards;
}
.slider.prev .list .item img{
z-index: 100;
}


@keyframes showThumbnail{
from{
width: 0;
opacity: 0;
}
}


.slider.next .thumbnail{
animation: effectNext .5s linear 1 forwards;
}

@keyframes effectNext{
from{
transform: translateX(150px);
}
}



/* Animation for prev button click */
.slider.prev .list .item:nth-child(2){
z-index: 2;
}

.slider.prev .list .item:nth-child(2) img{
animation: outFrame 0.5s linear 1 forwards;
position: absolute;
bottom: 0;
left: 0;
}
@keyframes outFrame{
to{
width: 150px;
height: 220px;
bottom: 50px;
left: 50%;
border-radius: 20px;
}
}

.slider.prev .thumbnail .item:nth-child(1){
overflow: hidden;
opacity: 0;
animation: showThumbnail .5s linear 1 forwards;
}
.slider.next .nextPrevArrows button,
.slider.prev .nextPrevArrows button{
pointer-events: none;
}


.slider.prev .list .item:nth-child(2) .content .title,
.slider.prev .list .item:nth-child(2) .content .type,
.slider.prev .list .item:nth-child(2) .content .description,
.slider.prev .list .item:nth-child(2) .content .buttons
{
animation: contentOut 1.5s linear 1 forwards!important;
}

@keyframes contentOut{
to{
transform: translateY(-150px);
filter: blur(20px);
opacity: 0;
}
}
@media screen and (max-width: 678px) {
.slider .list .item .content{
padding-right: 0;
}
.slider .list .item .content .title{
font-size: 50px;
}
}

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