<div class="slider">
  <button class="slider__prev">Previous</button>
  
  <p class="progress" aria-label="Slide 2 of 4">
    <span class="progress__current" aria-hidden="true">01</span>
    <span class="progress__last" aria-hidden="true">04</span>
  </p>
  
  <button class="slider__next">Next</button>
</div>

:root {
  --slider-progress: 0;
}

.slider {
  display: flex;
}

.progress {
  display: flex;
  align-items: center;
  margin: 0;
  font-weight: 700;
  font-size: 18px;
  width: 300px;
  
  &__current {
    margin-right: 10px;
  }
  
  &::before {
    content: '';
    flex-grow: 1;
    
    background-color: #eee;
    background-repeat: no-repeat;
   
    background-image: linear-gradient(to right, #000, #000 100%);
    background-size: 25% 100%;
    background-position: var(--slider-progress) 0;
   
    height: 1px;
    transition: .3s all;
    order: 1;
  }
 
  &__last {
    margin-left: 10px;
    order: 2;
  }
}

const slider = document.querySelector('.slider');
const sliderPrev = document.querySelector('.slider__prev');
const sliderNext = document.querySelector('.slider__next');

let current = 0;
let all = 3;

sliderNext.addEventListener('click', () => {
  current++;
  
  updateSlider();
});

sliderPrev.addEventListener('click', () => {
  current--;
  
  updateSlider();
});

function updateSlider() {
  if(current > all) {
    current = 0;
  }
  
  if(current < 0) {
    current = all;
  }
  
  slider.style.setProperty('--slider-progress', (current / all) * 100 + '%');
}