<div class="flex">
  <div ds-test="aaa" class="ccc"></div>
  <div ds-test="aaa" class="bbb"></div>
  <div ds-test="aaa" class="ddd"></div>
</div>

[ds-test*='aaa'] {
  width: 100px;
  height: 500px;
  background-color: khaki;
  border: 2px solid #000000;
}
.flex{
  height: 400px;
  overflow-y:scroll ;
}

  setTimeout(()=>{
      ScrollReveal().reveal('.flex .ddd',{ origin: 'right',distance: '100px',  container:'.flex'})

    },2000)