$(function(){
  
  // Bind an event to window.onhashchange that, when the hash changes, gets the
  // hash and adds the class "selected" to any matching nav link.
  $(window).bind( 'hashchange', function(){
    var hash = location.hash;
    
    // Iterate over all nav links, setting the "selected" class as-appropriate.
    $('#menu a').each(function(){
      var that = $(this);
      that[ that.attr( 'href' ) === hash ? 'addClass' : 'removeClass' ]( 'selected' );
    });
  })
  
  // Since the event is only triggered when the hash changes, we need to trigger
  // the event now, to handle the hash the page may have loaded with.
  $(window).trigger( 'hashchange' );
  
});