jQuery addPrior: Add the previous set's elements (before the last filter / traversal) to the current set, optionally filtering them. Supersedes jQuery's built-in .andSelf method.

jquery.ba-addprior.js

jQuery.fn.addPrior = function(selector) {
  var prior = this.prevObject;
  return this.add(selector == null ? prior : prior.filter(selector));
};

usage.js

// BASIC

// select UL + all LI children:
$("ul").children("li").addPrior()

// MORE COMPLEX

// select both first and last children:
$("li").filter(":first-child").addPrior(":last-child")

// FIND+FILTER

var elems = $(something);

// lame:
elems.find("li").add(elems.filter("li"))

// sexy:
elems.find("li").addPrior("li")

See jQuery ticket #9800 as well.