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Node.js Events Module

❮ Built-in Modules


Example

Make an event listener for an event called "scream", then provoke the event:

var events = require('events');
var eventEmitter = new events.EventEmitter();

eventEmitter.on('scream', function() {
console.log('A scream is detected!');
});
eventEmitter.emit('scream');
Run example »

Definition and Usage

The Events module provides a way of working with events.

In Node.js, all events are an instance of the EventEmitter object


Syntax

The syntax for including the Events module, and creating an EventEmitter in your application:

var events = require('events');
var eventEmitter = new events.EventEmitter();

EventEmitter Properties and Methods

Method Description
addListener() Adds the specified listener
defaultMaxListeners Sets the maximum number of listeners allowed for one event. Default is 10
emit() Call all the listeners registered with the specified name
eventNames() Returns an array containing all registered events
getMaxListeners() Returns the maximum number of listeners allowed for one event
listenerCount() Returns the number of listeners with the specified name
listeners() Returns an array of listeners with the specified name
on() Adds the specified listener
once() Adds the specified listener once. When the specified listener has been executed, the listener is removed
prependListener() Adds the specified listener as the first event with the specified name
prependOnceListener() Adds the specified listener as the first event with the specified name, once. When the specified listener has been executed, the listener is removed
removeAllListeners() Removes all listeners with the specified name, or ALL listeners if no name is specified
removeListener() Removes the specified listener with the specified name
setMaxListeners() Sets the maximum number of listeners allowed for one event. Default is 10

❮ Built-in Modules