Emit has two forms of deferred operations, ajax and events, in addition to the "immediate" mode. Under these modes the actual emit might occur far later than the original call due to pending events. Calling emit multiple times generally shouldn't have any effect other than moving the emitter to the most restrictive mode, i.e. events -> ajax -> "immediate". It's also possible for multiple `emit()` calls to occur prior to actually outputting data as the actual emit logic is run in a `setImmediate` call and the event continues executing as well as any queued immediate events.