58. get DOM tree height

Height of a tree is the maximum depth from root node. Empty root node have a height of 0.

If given DOM tree, can you create a function to get the height of it?

For the DOM tree below, we have a height of 4.

<div>  <div>    <p>      <button>Hello</button>    </p>  </div>  <p>    <span>World!</span>  </p></div>

Can you solve this both recursively and iteratively?