The previousElementSibling property returns the previous element of the specified element, in the same tree level.
The difference between this property and previousSibling, is that previousSibling returns the previous sibling node as an element node, a text node or a comment node, while previousElementSibling returns the previous sibling node as an element node (ignores text and comment nodes).
//Get the second li element
var liElement = document.getElementById( "target" ) ;
//Get the previous element (→ Text node (line feed and tab character))
var previousSibling = liElement.previousSibling ;
console.log("previousElementSibling::"+previousSibling.data);
console.log("previousSibling.previousElementSibling::",previousSibling.previousElementSibling);
//Get the previous element (→ <li> Element 3 </ li>)
var previousElementSibling = liElement.previousElementSibling ;
console.log("previousElementSibling::",previousElementSibling);
<ul>
<li>Element-1</li>↓
<li id="target">Element-2</li>
<li>Element-3</li>
</ul>