src code

instance method Element#previousSiblings 

Element#previousSiblings() → [Element…]

Collects all of element's previous siblings and returns them as an Array of elements.

Two elements are siblings if they have the same parent. So for example, the <head> and <body> elements are siblings (their parent is the <html> element). Previous-siblings are simply the ones which precede element in the document.

The returned Array reflects the siblings inversed order in the document (e.g. an index of 0 refers to the lowest sibling i.e., the one closest to element).

Note that all of Prototype's DOM traversal methods ignore text nodes and return element nodes only.

Examples
<ul>
  <li id="golden-delicious">Golden Delicious</li>
  <li id="mutsu">Mutsu</li>
  <li id="mcintosh">McIntosh</li>
  <li id="ida-red">Ida Red</li>
</ul>

Then:

$('mcintosh').previousSiblings();
// -> [li#mutsu, li#golden-delicious]
 $('golden-delicious').previousSiblings();
// -> []

This method can be called either as an instance method or as a generic method. If calling as a generic, pass the instance in as the first argument.