jQuery .offsetParent()

Given a jQuery object that represents a set of DOM elements, the .offsetParent() method allows us to search through the ancestors of these elements in the DOM tree and construct a new jQuery object wrapped around the closest positioned ancestor. An element is said to be positioned if it has a CSS position attribute of relative, absolute, or fixed. This information is useful for calculating offsets for performing animations and placing objects on the page.

Consider a page with a basic nested list on it, with a positioned element:

<ul class="level-1">
 <li class="item-i">I</li>
 <li class="item-ii" style="position: relative;">II
 <ul class="level-2">
 <li class="item-a">A</li>
 <li class="item-b">B
 <ul class="level-3">
 <li class="item-1">1</li>
 <li class="item-2">2</li>
 <li class="item-3">3</li>
 </ul>
 </li>
 <li class="item-c">C</li>
 </ul>
 </li>
 <li class="item-iii">III</li>
</ul>

If we begin at item A, we can find its positioned ancestor:

$( "li.item-a" ).offsetParent().css( "background-color", "red" );

This will change the color of list item II, which is positioned.