demo-review-star.html

<div class="block--demo">
  3/5　
  <span class="review-star" data-size="20" data-val="3" data-max="5"></span>
</div>
<div class="block--demo">
  4.2/5　
  <span class="review-star" data-size="20" data-val="4.2" data-max="5"></span>
</div>
<div class="block--demo">
  7.7/10　
  <span class="review-star" data-size="20" data-val="7.7" data-max="10"></span>
</div>
<div class="block--demo">
  1.5/3　
  <span class="review-star" data-size="20" data-val="1.5" data-max="3"></span>
</div>

<script src="path/to/review-star.js"></script>
<script>
  const review_star = new reviewStar();
</script>