1.4/1.4.1 and 1.4.2+ compatible event special .add method

jquery.event.special.foo.add.js

// 1.4.2 (new plugins, use this)
$.event.special.foo = {
  
  add: function( handleObj ) {
    // Do something when event is bound here!
    
    var old_handler = handleObj.handler;
    handleObj.handler = function(event) {
      // handleObj.type (string, 'foo' in this case)
      // handleObj.data (anything)
      // handleObj.namespace (string, sorted.namespace.list)
      
      // Modify event object here!
      old_handler.apply( this, arguments );
    };
  }
  
};

// 1.4, 1.4.1 and 1.4.2 (existing plugins, update for 1.4.2 this way)
$.event.special.foo = {
  
  add: function( handleObj ) {
    // Do something when event is bound here!
    
    var old_handler;
    
    function new_handler(event) {
      // Modify event object here!
      old_handler.apply( this, arguments );
    };
    
    // This may seem a little complicated, but it normalizes the special event
    // .add method between jQuery 1.4/1.4.1 and 1.4.2+
    if ( $.isFunction( handleObj ) ) {
      // 1.4, 1.4.1
      old_handler = handleObj;
      return new_handler;
    } else {
      // 1.4.2+
      old_handler = handleObj.handler;
      handleObj.handler = new_handler;
    }
  }
  
};

// 1.4, 1.4.1 (for reference only, the way it used to be)
$.event.special.foo = {
  
  add: function( handler, data, namespaces ) {
    // Do something when event is bound here!
    
    return function(event) {
      // handler.type (string, sorted.namespace.list, NOT the event type)
      // data (anything)
      // namespaces (sorted array of namespace strings)
      
      // Modify event object here!
      handler.apply( this, arguments );
    };
  }
  
};