Compare DOM tree order of elements

isBefore.js

// http://stackoverflow.com/questions/3860351/relative-position-in-dom-of-elements-in-jquery
// What this does is .add() the additional element (or selector)
// (which jQuery keeps in document order) and then checks if it's the second of the two.

(function($) {
  $.fn.isBefore = function(elem) {
    if(typeof(elem) == "string") elem = $(elem);
    return this.add(elem).index(elem) > 0;
  }
})(jQuery)

$("#p1").isBefore("#p2");