Вопрос со слайдером на чистом JS.Почему то не работает

function slider(){
    const sliderField = document.querySelector('.slider__inner'),
          slides = document.querySelectorAll('.slider__item'),
          prevSlide = document.querySelector('.prev-slide'),
          nextSlide = document.querySelector('.next-slide');

    let slideIndex = 0;

    function showSlide(){
        if(slideIndex > slides.length - 1) {
            slideIndex = 0;
        }else if(slideIndex < 0) {
            slideIndex = slides.length - 1;
        } 
        slides.forEach( (slide, index) => {
            if(slideIndex === index) {
                slide.style.transform = 'translateX(0)';
            } else if( slideIndex < index) {
                slide.style.transform = 'translateX(-100%)';
            } else if(slideIndex > index) {
                slide.style.transform = 'translateX(100%)';
            }
        });
        
    }

    prevSlide.addEventListener('click', ()=> {
        slideIndex -= 1;
        showSlide();
   
    });

    nextSlide.addEventListener('click', ()=> {
        slideIndex += 1;
        showSlide();
   
    });
}