onload animation delay of child elements of a div with js?

i have div, inside which i have made 3 card inside it and animated it as slide in. I can delay animation using nth child, but i want to do it with java script .children property and apply animation delay as --> index + 's' [my code] (https://codepen.io/beastop/pen/mdVMNgY)

<div class="container">
  <div class="card"></div>
  <div class="card"></div>
      <div class="card"></div>
</div>