<h1>Vælg en værdi</h1>
<form>
  <label for="slider">Volume</label>
  <div class="slider-group">
    <input id="slider" type="range" value="0" min="0" max="100" />
    <output for="slider" id="slider-value">0</output>
  </div>
</form>

const sliderInput = document.querySelector("#slider");
const sliderValue = document.querySelector("#slider-value");

function updateHeadingValue() {
  sliderValue.value = sliderInput.value;
}

sliderInput.addEventListener("input", updateHeadingValue);