100vh height 100%

index.html

<script>
  function setIntroHeight(){
    var vh = window.innerHeight * 0.01;
    document.documentElement.style.setProperty('--vh', vh + 'px');
  }
  setIntroHeight();
</script>

<style>
.block{
  height: 100vh;
  height: calc(var(--vh, 1vh) * 100);
}
</style>