Find next (or previous) matching element in the DOM, wherever it is in the tree.

nextAnywhere.js

(function($) {

  var getNext = function(item) {
    if(item.length === 0) return null;
    if(item.next().length > 0) return item.next();
    return getNext(item.parent());
  };

  var getPrev = function(item) {
    if(item.length === 0) return null;
    if(item.prev().length > 0) return item.prev();
    return getPrev(item.parent());
  };

  $.fn.nextAnywhere = function(selector) {
    var next = getNext(this);
    while(next && next.length > 0) {
      if(next.is(selector)) return next;
      var el = next.find(selector);
      if(el.length > 0) return el.first();
      next = getNext(next);
    }
    return null;
  };

  $.fn.prevAnywhere = function(selector) {
    var prev = getPrev(this);
    while(prev && prev.length > 0) {
      if(prev.is(selector)) return prev;
      var el = prev.find(selector);
      if(el.length > 0) return el.last();
      prev = getPrev(prev);
    }
    return null;
  };

})(jQuery);