:headerBelow and :headerAbove

jquery.headersAboveBelow.js

// jQuery custom selectors for headers above (lower <h> tag) or below (higher <h> tag) given an arbitrary level
(function( $ ) {
  $.extend($.expr[':'],{
    // selects all the headers below the passed index.  So 2 matches <h3>, <h4>, <h5>.
    headerBelow: function( elem, i, match ) { 
      if ( /h\d/i.test( elem.nodeName ) )  {
        var level= parseInt( match[ 3 ], 10 ) + 1,  str = "h["+ level +"-5]", re = new RegExp( str, "i" ), ret ;
        return re.test( elem.nodeName ); 
      }
      return false;
    },
    // selects all the headers above the passed index.  So 3 matches <h1> and <h2>.
    headerAbove: function( elem, i, match ) { 
      if ( /h\d/i.test( elem.nodeName ) )  {		
        var level= ( parseInt( match [ 3 ], 10 ) - 1 ) || 1, str = "h[1-"+ level +"]", re = new RegExp( str, "i" ) ;
        return re.test( elem.nodeName ); 
      }
      return false;
    }
  });
});