code: function() {
  				if ( list ) {
  					var length = list.length;
  					add( arguments );
  					// Do we need to add the callbacks to the
  					// current firing batch?
  					if ( firing ) {
  						firingLength = list.length;
  					// With memory, if we're not firing then
  					// we should call right away, unless previous
  					// firing was halted (stopOnFalse)
  					} else if ( memory && memory !== true ) {
  						firingStart = length;
  						fire( memory[ 0 ], memory[ 1 ] );
  					}
  				}
  				return this;
  			}
docs: Add a callback or a collection of callbacks to the list