To check element is descendant of parent element

isDescendent.js

/* Returns true incase of `child` element is child element of `parent` element */
function isDescendant(parent, child) {
  let node = child.parentNode;
  while (node != null) {
    if (node == parent) {
      return true;
    }
    node = node.parentNode;
  }
  return false;
}