elementContains

Checks if the parent element contains the child element.

• Check that parent is not the same element as child.
• Use Node.contains() to check if the parent element contains the child element.

const elementContains = (parent, child) =>
  parent !== child && parent.contains(child);

elementContains(
  document.querySelector('head'),
  document.querySelector('title')
);
// true
elementContains(document.querySelector('body'), document.querySelector('body'));
// false