Range slider with value bubble

<label class="range-field">
  <span class="range-title">Monthly budget</span>
  <span class="range-wrap">
    <output class="range-bubble" for="budget">$400</output>
    <input id="budget" class="range" type="range" min="0" max="1000" step="50" value="400">
  </span>
  <span class="range-scale"><span>$0</span><span>$1,000</span></span>
</label>

.range-field { width: min(380px, 100%); display: grid; gap: 10px; font: 14px system-ui, sans-serif; }
.range-title { font-weight: 600; }
.range-wrap { position: relative; padding-top: 34px; }
.range-scale { display: flex; justify-content: space-between; color: var(--muted); font-size: 12px; }

/* Reset the native look, then draw our own track and thumb.
   --fill (0–100%) is set by the script and colors the part left of the thumb. */
.range {
  appearance: none;
  width: 100%;
  height: 8px;
  margin: 0;
  border-radius: 99px;
  background: linear-gradient(90deg, var(--brand) var(--fill, 40%), var(--surface-2) var(--fill, 40%));
  cursor: pointer;
}
.range::-webkit-slider-thumb {
  appearance: none;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: #fff;
  border: 3px solid var(--brand);
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.25);
}
.range::-moz-range-thumb {
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: #fff;
  border: 3px solid var(--brand);
}
.range:focus-visible { outline: 2px solid var(--brand); outline-offset: 6px; }

/* The bubble sits above the thumb. Its left edge is calculated so it stays centered
   on the thumb even at the ends (the thumb doesn't travel the full width). */
.range-bubble {
  position: absolute;
  top: 0;
  left: calc(var(--fill, 40%) + (12px - var(--fill-ratio, 0.4) * 24px));
  transform: translateX(-50%);
  padding: 3px 9px;
  border-radius: 8px;
  font: 600 13px system-ui, sans-serif;
  color: #fff;
  background: var(--brand);
  white-space: nowrap;
  font-variant-numeric: tabular-nums;
}

// Range slider: keeps the filled track and the bubble in step with the value.

document.querySelectorAll('.range-field').forEach((field) => {
  const range = field.querySelector('.range');
  const bubble = field.querySelector('.range-bubble');
  const formatMoney = (value) => `$${Number(value).toLocaleString()}`;

  function update() {
    const ratio = (range.value - range.min) / (range.max - range.min); // 0 at the left, 1 at the right
    field.style.setProperty('--fill', `${ratio * 100}%`);
    field.style.setProperty('--fill-ratio', ratio);
    bubble.textContent = formatMoney(range.value);
    range.setAttribute('aria-valuetext', formatMoney(range.value)); // read "$400", not "400"
  }

  range.addEventListener('input', update);
  update();
});