EventEmitter
Related Docs:
object EventEmitter
| package events
Alias for emitter.on(eventName, listener).
Alias for emitter.on(eventName, listener).
emitter.addListener(eventName, listener)
on()
Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each.
Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each.
Returns true if the event had listeners, false otherwise.
the event name
the event arguments
emitter.emit(name[, arg1][, arg2][, ...])
Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to EventEmitter.defaultMaxListeners.
Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to EventEmitter.defaultMaxListeners.
emitter.getMaxListeners()
setMaxListeners()
Returns the number of listeners listening to the event named eventName.
Returns the number of listeners listening to the event named eventName.
emitter.listenerCount(eventName)
Returns a copy of the array of listeners for the event named eventName.
Returns a copy of the array of listeners for the event named eventName.
emitter.listeners(eventName)
Adds the listener function to the end of the listeners array for the event named eventName.
Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.
Returns a reference to the EventEmitter so calls can be chained.
emitter.on(eventName, listener)
Adds a one time listener function for the event named eventName.
Adds a one time listener function for the event named eventName. This listener is invoked only the next time eventName is triggered, after which it is removed.
emitter.once(eventName, listener)
Removes all listeners, or those of the specified eventName.
Removes all listeners, or those of the specified eventName.
Note that it is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).
Returns a reference to the EventEmitter so calls can be chained.
emitter.removeAllListeners([eventName])
Removes all listeners, or those of the specified eventName.
Removes all listeners, or those of the specified eventName.
Note that it is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).
Returns a reference to the EventEmitter so calls can be chained.
emitter.removeAllListeners([eventName])
Removes the specified listener from the listener array for the event named eventName.
Removes the specified listener from the listener array for the event named eventName. removeListener will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified eventName, then removeListener must be called multiple times to remove each instance.
Note that once an event has been emitted, all listeners attached to it at the time of emitting will be called in order. This implies that any removeListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them from emit() in progress. Subsequent events will behave as expected.
emitter.removeListener(eventName, listener)
By default EventEmitters will print a warning if more than 10 listeners are added for a particular event.
By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. Obviously, not all events should be limited to just 10 listeners. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) for to indicate an unlimited number of listeners.
Returns a reference to the EventEmitter so calls can be chained.
emitter.setMaxListeners(n)
Much of the Node.js core API is built around an idiomatic asynchronous event-driven architecture in which certain kinds of objects (called "emitters") periodically emit named events that cause Function objects ("listeners") to be called.
The EventEmitter class is defined and exposed by the events module
https://nodejs.org/api/events.html