Class EventEmitter

When an EventEmitter instance experiences an error, the typical action is to emit an ‘error’ event. Error events are treated as a special case in node. If there is no listener for it, then the default action is to print a stack trace and exit the program. All EventEmitters emit the event ‘newListener’ when new listeners are added.

Constructor

class EventEmitter()

Methods

addListener

EventEmitter#addListener(type, listener)

Arguments:

• type (String) – The event name
• listener (Function) – The listener function

Returns EventEmitter:  

Adds a listener to the end of the listeners array for the specified event.

emit

EventEmitter#emit(event[, arg, arg2])

Arguments:

• event (String) – The event name
• arg,arg2 – The arguments to pass

Execute each of the listeners in order with the supplied arguments.

listeners

EventEmitter#listeners(type)

Arguments:

• type (String) – The event name

Returns EventEmitter:  

Instance

Returns an array of listeners for the specified event. This array can be manipulated, e.g. to remove listeners.

on

EventEmitter#on()

See also

EventEmitter#addListener

once

EventEmitter#once(type, listener)

Arguments:

• type (String) – The event name
• listener (Function) – The listener function

Returns EventEmitter:  

Instance

Adds a one time listener for the event. This listener is invoked only the next time the event is fired, after which it is removed.

removeAllListeners

EventEmitter#removeAllListeners(type)

Arguments:

• type (String) – The event name

Returns EventEmitter:  

Instance

Removes all listeners, or those of the specified event.

removeListener

EventEmitter#removeListener(type, listener)

Arguments:

• type (String) – The event name
• listener (Function) – The listener function

Returns EventEmitter:  

Instance

Remove a listener from the listener array for the specified event. Caution: changes array indices in the listener array behind the listener.

setMaxListeners

EventEmitter#setMaxListeners(n)

Arguments:

• n (Number) –

By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default which helps finding memory leaks. Obviously not all Emitters should be limited to 10. This function allows that to be increased. Set to zero for unlimited.