code: function( type, obj ) {
  		var tmp,
  			count = 1,
  			defer = jQuery.Deferred(),
  			elements = this,
  			i = this.length,
  			resolve = function() {
  				if ( !( --count ) ) {
  					defer.resolveWith( elements, [ elements ] );
  				}
  			};
  
  		if ( typeof type !== "string" ) {
  			obj = type;
  			type = undefined;
  		}
  		type = type || "fx";
  
  		while ( i-- ) {
  			tmp = dataPriv.get( elements[ i ], type + "queueHooks" );
  			if ( tmp && tmp.empty ) {
  				count++;
  				tmp.empty.add( resolve );
  			}
  		}
  		resolve();
  		return defer.promise( obj );
  	}
docs: Get a promise resolved when queues of a certain type are emptied (fx is the type by default)