itemClickHandler is in the scope of B, so that certainly shouldn't be accessible in A.
Generally, its good to use a common parent container C as a mediator between A and B. Something happens in A, so A dispatches an event "somethingHappened". C is listening for A's event. When C receives that event, calls a function on B so that B can respond to whatever happened in B.
Josh Tynjala | Feathers