Drag-Active Thumb

<div class="nuda-actthumb">
  <div class="nuda-actthumb__track">
    <div class="nuda-actthumb__fill" style="width:45%"></div>
    <div class="nuda-actthumb__thumb" style="left:45%">
      <span class="nuda-actthumb__halo"></span>
    </div>
  </div>
</div>

const slider = document.querySelector('.nuda-actthumb');
const thumb = slider.querySelector('.nuda-actthumb__thumb');

thumb.addEventListener('pointerdown', () => slider.classList.add('is-dragging'));
window.addEventListener('pointerup', () => slider.classList.remove('is-dragging'));

.nuda-actthumb {
  width: 100%;
  max-width: 220px;
  padding: 14px 12px;
}

.nuda-actthumb__track {
  position: relative;
  height: 4px;
  background: rgba(255,255,255,.08);
  border-radius: 99px;
}

.nuda-actthumb__fill {
  position: absolute;
  left: 0;
  top: 0;
  height: 100%;
  background: #e4ff54;
  border-radius: 99px;
}

.nuda-actthumb__thumb {
  position: absolute;
  top: 50%;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: #e4ff54;
  transform: translate(-50%,-50%);
  cursor: grab;
  transition: transform .25s;
}

.nuda-actthumb__halo {
  position: absolute;
  inset: -12px;
  border-radius: 50%;
  background: rgba(228,255,84,.18);
  opacity: 0;
  transform: scale(.6);
  transition: opacity .25s,transform .35s cubic-bezier(.16,1,.3,1);
}

.nuda-actthumb.is-dragging .nuda-actthumb__thumb {
  transform: translate(-50%,-50%) scale(1.25);
  cursor: grabbing;
}

.nuda-actthumb.is-dragging .nuda-actthumb__halo {
  opacity: 1;
  transform: scale(1);
  animation: _haloPulse 1.6s ease-in-out infinite;
}

@keyframes _haloPulse {
  0%,100% {
    transform: scale(1);
    opacity: 1;
  }
  50% {
    transform: scale(1.15);
    opacity: .6;
  }
}

@media (prefers-reduced-motion:reduce) {
  .nuda-actthumb.is-dragging .nuda-actthumb__halo {
    animation: none;
  }
}