Search for all parents of elements in JavaScript

Given an element:

<header>
	<div>
		<p>
			<span id="elem"></span>
		</p>
	</div>
</header>

Find the closest parent of this element, which is the div tag.

Given an element:

<header>
	<div class="www">
		<p class="www">
			<span id="elem"></span>
		</p>
	</div>
</header>

Find the closest parent of this element, which is an element with the class www.