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@webda/coreReadme | API


Class: Authentication<T, E>

This class is known as the Authentication module It handles OAuth for several providers for now (Facebook, Google, Amazon, GitHub and Twitter) It also handles email authentication with prevalidation or postvalidation of the email

It requires two Store to work one idents and one users

The parameters are

  providerName: {
clientID: '...',
clientSecret: '...',
scope: ''
},
email: {
postValidation: true|false // If postValidation=true, account created without email verification
}
url: 'url' // By default /auth

Webda Modda

Extends

Type parameters

T extends AuthenticationParameters = AuthenticationParameters

E extends AuthenticationEvents = AuthenticationEvents

Constructors

new Authentication(webda, name, params)

new Authentication<T, E>(webda, name, params): Authentication<T, E>

Parameters

webda: Core<CoreEvents>

The main instance of Webda

name: string

The name of the service

params: DeepPartial<T>= {}

The parameters block define in the configuration file

Returns

Authentication<T, E>

Inherited from

Service.constructor

Source

packages/core/src/services/service.ts:334

Properties

_createException

_createException: string

Inherited from

Service._createException

Source

packages/core/src/services/service.ts:315


_identModel

_identModel: CoreModelDefinition<Ident>

Source

packages/core/src/services/authentication.ts:238


_initException

_initException: any = undefined

Inherited from

Service._initException

Source

packages/core/src/services/service.ts:317


_initTime

_initTime: number

Inherited from

Service._initTime

Source

packages/core/src/services/service.ts:316


_name

protected _name: string

Service name

Inherited from

Service._name

Source

packages/core/src/services/service.ts:308


_passwordVerifier

_passwordVerifier: PasswordVerifier

Source

packages/core/src/services/authentication.ts:245


_userModel

_userModel: CoreModelDefinition<User>

Source

packages/core/src/services/authentication.ts:239


_webda

protected _webda: Core<CoreEvents>

Webda Core object

Inherited from

Service._webda

Source

packages/core/src/services/service.ts:304


cryptoService

cryptoService: CryptoService<CryptoServiceParameters>

Used for hmac

Source

packages/core/src/services/authentication.ts:244


logger

protected logger: Logger

Logger with class context

Inherited from

Service.logger

Source

packages/core/src/services/service.ts:321


metrics

metrics: Object

Get metrics

Type declaration

login

login: Counter<string>

loginFailed?

loginFailed?: Counter<string>

logout

logout: Counter<string>

recovered?

recovered?: Counter<string>

recovery?

recovery?: Counter<string>

registration?

registration?: Counter<string>

Overrides

Service.metrics

Source

packages/core/src/services/authentication.ts:248


parameters

protected parameters: T

Hold the parameters for your service

It will be bring from the webda.config.json

Inherited from

Service.parameters

Source

packages/core/src/services/service.ts:314


providers

providers: Set<string>

Source

packages/core/src/services/authentication.ts:246


captureRejectionSymbol

static readonly captureRejectionSymbol: typeof captureRejectionSymbol

Inherited from

Service.captureRejectionSymbol

Source

packages/core/node_modules/@types/node/events.d.ts:328


captureRejections

static captureRejections: boolean

Sets or gets the default captureRejection value for all emitters.

Inherited from

Service.captureRejections

Source

packages/core/node_modules/@types/node/events.d.ts:333


defaultMaxListeners

static defaultMaxListeners: number

Inherited from

Service.defaultMaxListeners

Source

packages/core/node_modules/@types/node/events.d.ts:334


errorMonitor

static readonly errorMonitor: typeof errorMonitor

This symbol shall be used to install a listener for only monitoring 'error' events. Listeners installed using this symbol are called before the regular 'error' listeners are called.

Installing a listener using this symbol does not change the behavior once an 'error' event is emitted, therefore the process will still crash if no regular 'error' listener is installed.

Inherited from

Service.errorMonitor

Source

packages/core/node_modules/@types/node/events.d.ts:327

Methods

__clean()

__clean(): Promise<void>

Clean the service data, can only be used in test mode

Returns

Promise<void>

Inherited from

Service.__clean

Abstract

Source

packages/core/src/services/service.ts:642


_getMe()

_getMe(ctx): Promise<void>

Return current user

Parameters

ctx: OperationContext<any, any>

Returns

Promise<void>

Source

packages/core/src/services/authentication.ts:482


_handleEmail()

_handleEmail(ctx): Promise<any>

Handle the POST /auth/email

Parameters

ctx: WebContext<LoginBody, any>

Returns

Promise<any>

Source

packages/core/src/services/authentication.ts:942


_handleEmailCallback()

_handleEmailCallback(ctx): Promise<void>

Callback to validate an email address

Parameters

ctx: WebContext<any, any>

Returns

Promise<void>

Source

packages/core/src/services/authentication.ts:728


_listAuthentications()

_listAuthentications(ctx): Promise<void>

Handle both list of available authentication and logout with method 'DELETE'

Parameters

ctx: WebContext<any, any>

Returns

Promise<void>

Source

packages/core/src/services/authentication.ts:521


_passwordRecovery()

_passwordRecovery(ctx): Promise<void>

Parameters

ctx: WebContext<PasswordRecoveryBody, any>

Returns

Promise<void>

Source

packages/core/src/services/authentication.ts:690


_passwordRecoveryEmail()

_passwordRecoveryEmail(ctx): Promise<void>

Manage password recovery

Parameters

ctx: WebContext<any, any>

Returns

Promise<void>

Source

packages/core/src/services/authentication.ts:656


_sendEmailValidation()

_sendEmailValidation(ctx): Promise<void>

Send or resend an email to validate the email address

Parameters

ctx: any

Returns

Promise<void>

Throws

409 if ident is linked to someone else

Throws

412 if the email is already validated

Throws

429 if a validation email has been sent recently

Source

packages/core/src/services/authentication.ts:445


_verifyPassword()

_verifyPassword(password, user?): Promise<void>

Parameters

password: string

user?: User

Returns

Promise<void>

Source

packages/core/src/services/authentication.ts:677


addListener()

addListener(eventName, listener): this

Alias for emitter.on(eventName, listener).

Parameters

eventName: string | symbol

listener: (...args) => void

Returns

this

Inherited from

Service.addListener

Since

v0.1.26

Source

packages/core/node_modules/@types/node/events.d.ts:354


addProvider()

addProvider(name): void

Add a provider to the oauth scheme

Parameters

name: string

Returns

void

Source

packages/core/src/services/authentication.ts:401


addRoute()

protected addRoute(url, methods, executer, openapi, override): void

Add a route dynamicaly

Parameters

url: string

of the route can contains dynamic part like {uuid}

methods: HttpMethodType[]

executer: Function

Method to execute for this route

openapi: OpenAPIWebdaDefinition= {}

override: boolean= false

Returns

void

Inherited from

Service.addRoute

Source

packages/core/src/services/service.ts:482


authorizeClientEvent()

authorizeClientEvent(_event, _context): boolean

Authorize a public event subscription

Parameters

_event: string

_context: OperationContext<any, any>

Returns

boolean

Inherited from

Service.authorizeClientEvent

Source

packages/core/src/services/service.ts:438


checkPassword()

checkPassword(hash, pass): boolean

Check the password match the stored hash

Parameters

hash: string

generate prior by hashPassword

pass: string

Returns

boolean

Source

packages/core/src/services/authentication.ts:841


createUserWithIdent()

createUserWithIdent(provider, identId, profile): Promise<void>

Create a new User with the link ident

Parameters

provider: string

identId: string

profile: any= {}

Returns

Promise<void>

Source

packages/core/src/services/authentication.ts:603


emit()

emit<Key>(event, data): boolean

Override to allow capturing long listeners

Type parameters

Key extends string | number | symbol

Parameters

event: symbol | Key

data: E[Key]

Returns

boolean

Inherited from

Service.emit

Source

packages/core/src/services/service.ts:596


emitSync()

emitSync<Key>(event, data): Promise<any[]>

Emit the event with data and wait for Promise to finish if listener returned a Promise

Type parameters

Key extends string | number | symbol

Parameters

event: Key

data: E[Key]

Returns

Promise<any[]>

Inherited from

Service.emitSync

Source

packages/core/src/services/service.ts:588


eventNames()

eventNames(): (string | symbol)[]

Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or Symbols.

const EventEmitter = require('events');
const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});

const sym = Symbol('symbol');
myEE.on(sym, () => {});

console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]

Returns

(string | symbol)[]

Inherited from

Service.eventNames

Since

v6.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:669


generateEmailValidationToken()

generateEmailValidationToken(user, email): Promise<string>

Parameters

user: string

email: string

Returns

Promise<string>

Source

packages/core/src/services/authentication.ts:1033


getClientEvents()

getClientEvents(): string[]

Return the events that an external system can subscribe to

Returns

string[]

Inherited from

Service.getClientEvents

Source

packages/core/src/services/service.ts:429


getIdentStore()

getIdentStore<K>(): Store<K, StoreParameters, StoreEvents>

Get the user store

Type parameters

K extends Ident = Ident

Returns

Store<K, StoreParameters, StoreEvents>

Source

packages/core/src/services/authentication.ts:276


getMailMan()

getMailMan(): Mailer<MailerParameters>

Returns

Mailer<MailerParameters>

Source

packages/core/src/services/authentication.ts:892


getMaxListeners()

getMaxListeners(): number

Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to defaultMaxListeners.

Returns

number

Inherited from

Service.getMaxListeners

Since

v1.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:526


getMetric()

getMetric<T>(type, configuration): T

Add service name label

Type parameters

T = Counter<string> | Histogram<string> | Gauge<string>

Parameters

type: Constructor<T, [MetricConfiguration<T>]>

configuration: MetricConfiguration<T>

Returns

T

Inherited from

Service.getMetric

Source

packages/core/src/services/service.ts:414


getName()

getName(): string

Get service name

Returns

string

Inherited from

Service.getName

Source

packages/core/src/services/service.ts:633


getOpenApiReplacements()

getOpenApiReplacements(): any

Return variables for replacement in openapi

Returns

any

Inherited from

Service.getOpenApiReplacements

Source

packages/core/src/services/service.ts:507


getOperationId()

getOperationId(id): string

If undefined is returned it cancel the operation registration

Parameters

id: string

Returns

string

Inherited from

Service.getOperationId

Source

packages/core/src/services/service.ts:471


getParameters()

getParameters(): T

Get the service parameters

Returns

T

Inherited from

Service.getParameters

Source

packages/core/src/services/service.ts:359


getPasswordRecoveryInfos()

getPasswordRecoveryInfos(uuid, interval): Promise<PasswordRecoveryInfos>

Parameters

uuid: string | User

interval: number= undefined

Returns

Promise<PasswordRecoveryInfos>

Source

packages/core/src/services/authentication.ts:630


getService()

getService<K>(service): K

Return a webda service

Type parameters

K extends Service<ServiceParameters, Events>

Parameters

service: string

name to retrieve

Returns

K

Inherited from

Service.getService

Source

packages/core/src/services/service.ts:626


getUrl()

getUrl(url, methods): string

Ensure email is enabled for all emails routes

Parameters

url: string

methods: HttpMethodType[]

Returns

string

Overrides

Service.getUrl

Source

packages/core/src/services/authentication.ts:409


getUserStore()

getUserStore<K>(): Store<K, StoreParameters, StoreEvents>

Get the user store

Type parameters

K extends User = User

Returns

Store<K, StoreParameters, StoreEvents>

Source

packages/core/src/services/authentication.ts:268


getWebda()

getWebda(): Core<CoreEvents>

Return WebdaCore

Returns

Core<CoreEvents>

Inherited from

Service.getWebda

Source

packages/core/src/services/service.ts:366


handleLogin()

protected handleLogin(ctx, ident): Promise<void>

Handle a user login request

Parameters

ctx: WebContext<LoginBody, any>

ident: Ident

Returns

Promise<void>

Source

packages/core/src/services/authentication.ts:902


hashPassword()

hashPassword(pass): string

Hash the password according to good practices

Parameters

pass: string

to hash

Returns

string

Source

packages/core/src/services/authentication.ts:850


init()

init(): Promise<Authentication<T, E>>

Will be called after all the Services are created

Returns

Promise<Authentication<T, E>>

Inherited from

Service.init

Abstract

Source

packages/core/src/services/service.ts:570


initMetrics()

initMetrics(): void

Returns

void

Overrides

Service.initMetrics

Source

packages/core/src/services/authentication.ts:365


initOperations()

initOperations(): void

Init the operations

Returns

void

Inherited from

Service.initOperations

Source

packages/core/src/services/service.ts:528


initRoutes()

initRoutes(): void

Init the routes

Returns

void

Inherited from

Service.initRoutes

Source

packages/core/src/services/service.ts:514


listenerCount()

listenerCount(eventName): number

Returns the number of listeners listening to the event named eventName.

Parameters

eventName: string | symbol

The name of the event being listened for

Returns

number

Inherited from

Service.listenerCount

Since

v3.2.0

Source

packages/core/node_modules/@types/node/events.d.ts:616


listeners()

listeners(eventName): Function[]

Returns a copy of the array of listeners for the event named eventName.

server.on('connection', (stream) => {
console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]

Parameters

eventName: string | symbol

Returns

Function[]

Inherited from

Service.listeners

Since

v0.1.26

Source

packages/core/node_modules/@types/node/events.d.ts:539


loadParameters()

loadParameters(params): AuthenticationParameters

Load the parameters for a service

Parameters

params: any

Returns

AuthenticationParameters

Overrides

Service.loadParameters

Source

packages/core/src/services/authentication.ts:260


log()

log(level, ...args): void

Parameters

level: WorkerLogLevel

to log

• ...args: any[]

Returns

void

Inherited from

Service.log

Source

packages/core/src/services/service.ts:662


login()

login(ctx, user, ident, provider): Promise<any[]>

Login a user

Parameters

ctx: WebContext<any, any>

user: string | User

ident: Ident

provider: string

Returns

Promise<any[]>

Source

packages/core/src/services/authentication.ts:872


logout()

logout(ctx): Promise<void>

Logout user

Parameters

ctx: WebContext<any, any>

Returns

Promise<void>

Source

packages/core/src/services/authentication.ts:857


off()

off(eventName, listener): this

Alias for emitter.removeListener().

Parameters

eventName: string | symbol

listener: (...args) => void

Returns

this

Inherited from

Service.off

Since

v10.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:499


on()

on<Key>(event, listener): this

Type the listener part

Type parameters

Key extends string | number | symbol

Parameters

event: symbol | Key

listener: (evt) => void

Returns

this

Inherited from

Service.on

Source

packages/core/src/services/service.ts:607


onAsync()

onAsync<Key>(event, listener, queue): void

Listen to an event as on(...) would do except that it will be asynchronous

Type parameters

Key extends string | number | symbol

Parameters

event: Key

listener: (evt) => void

queue: string= undefined

Name of queue to use, can be undefined, queue name are used to define differents priorities

Returns

void

Inherited from

Service.onAsync

Source

packages/core/src/services/service.ts:618


onIdentLogin()

onIdentLogin(ctx, provider, identId, profile, tokens): Promise<void>

Parameters

ctx: WebContext<any, any>

provider: string

identId: string

profile: any

tokens: any= undefined

Returns

Promise<void>

Source

packages/core/src/services/authentication.ts:531


once()

once(eventName, listener): this

Adds a one-timelistener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.

server.once('connection', (stream) => {
console.log('Ah, we have our first user!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. Theemitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a

Parameters

eventName: string | symbol

The name of the event.

listener: (...args) => void

The callback function

Returns

this

Inherited from

Service.once

Since

v0.3.0

Source

packages/core/node_modules/@types/node/events.d.ts:414


prependListener()

prependListener(eventName, listener): this

Adds the listener function to the beginning 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 eventNameand listener will result in the listener being added, and called, multiple times.

server.prependListener('connection', (stream) => {
console.log('someone connected!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

eventName: string | symbol

The name of the event.

listener: (...args) => void

The callback function

Returns

this

Inherited from

Service.prependListener

Since

v6.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:634


prependOnceListener()

prependOnceListener(eventName, listener): this

Adds a one-timelistener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this listener is removed, and then invoked.

server.prependOnceListener('connection', (stream) => {
console.log('Ah, we have our first user!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

eventName: string | symbol

The name of the event.

listener: (...args) => void

The callback function

Returns

this

Inherited from

Service.prependOnceListener

Since

v6.0.0

Source

packages/core/node_modules/@types/node/events.d.ts:650


rawListeners()

rawListeners(eventName): Function[]

Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));

// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];

// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();

// Logs "log once" to the console and removes the listener
logFnWrapper();

emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');

// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');

Parameters

eventName: string | symbol

Returns

Function[]

Inherited from

Service.rawListeners

Since

v9.4.0

Source

packages/core/node_modules/@types/node/events.d.ts:569


registerUser()

registerUser(ctx, data, identId, user): Promise<User>

Parameters

ctx: WebContext<any, any>

data: any

identId: string

user: User= undefined

Returns

Promise<User>

Source

packages/core/src/services/authentication.ts:612


reinit()

reinit(config): Promise<Authentication<T, E>>

Parameters

config: DeepPartial<T>

new parameters for the service

Returns

Promise<Authentication<T, E>>

Inherited from

Service.reinit

Source

packages/core/src/services/service.ts:579


removeAllListeners()

removeAllListeners(event?): this

Removes all listeners, or those of the specified eventName.

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 that calls can be chained.

Parameters

event?: string | symbol

Returns

this

Inherited from

Service.removeAllListeners

Since

v0.1.26

Source

packages/core/node_modules/@types/node/events.d.ts:510


removeListener()

removeListener(eventName, listener): this

Removes the specified listener from the listener array for the event namedeventName.

const callback = (stream) => {
console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);

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.

Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that anyremoveListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them fromemit() in progress. Subsequent events behave as expected.

const myEmitter = new MyEmitter();

const callbackA = () => {
console.log('A');
myEmitter.removeListener('event', callbackB);
};

const callbackB = () => {
console.log('B');
};

myEmitter.on('event', callbackA);

myEmitter.on('event', callbackB);

// callbackA removes listener callbackB but it will still be called.
// Internal listener array at time of emit [callbackA, callbackB]
myEmitter.emit('event');
// Prints:
// A
// B

// callbackB is now removed.
// Internal listener array [callbackA]
myEmitter.emit('event');
// Prints:
// A

Because listeners are managed using an internal array, calling this will change the position indices of any listener registered after the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the emitter.listeners() method will need to be recreated.

When a single function has been added as a handler multiple times for a single event (as in the example below), removeListener() will remove the most recently added instance. In the example the once('ping')listener is removed:

const ee = new EventEmitter();

function pong() {
console.log('pong');
}

ee.on('ping', pong);
ee.once('ping', pong);
ee.removeListener('ping', pong);

ee.emit('ping');
ee.emit('ping');

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

eventName: string | symbol

listener: (...args) => void

Returns

this

Inherited from

Service.removeListener

Since

v0.1.26

Source

packages/core/node_modules/@types/node/events.d.ts:494


resolve()

resolve(): this

Resolve parameters Call initRoutes and initBeanRoutes

Returns

this

Inherited from

Service.resolve

Source

packages/core/src/services/service.ts:388


sendRecoveryEmail()

sendRecoveryEmail(ctx, user, email): Promise<any>

Send an email to recover the user password

Parameters

ctx: WebContext<any, any>

user: any

email: string

Returns

Promise<any>

Source

packages/core/src/services/authentication.ts:783


sendValidationEmail()

sendValidationEmail(ctx, email): Promise<any>

Send an email to validate the user email by sending a unique link to his email

Parameters

ctx: WebContext<any, any>

email: string

Returns

Promise<any>

Source

packages/core/src/services/authentication.ts:809


setMaxListeners()

setMaxListeners(n): this

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. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set toInfinity (or 0) to indicate an unlimited number of listeners.

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

n: number

Returns

this

Inherited from

Service.setMaxListeners

Since

v0.3.5

Source

packages/core/node_modules/@types/node/events.d.ts:520


stop()

stop(): Promise<void>

Shutdown the current service if action need to be taken

Returns

Promise<void>

Inherited from

Service.stop

Source

packages/core/src/services/service.ts:373


toJSON()

toJSON(): string

Prevent service to be serialized

Returns

string

Inherited from

Service.toJSON

Source

packages/core/src/services/service.ts:560


toPublicJSON()

toPublicJSON(object): string

Convert an object to JSON using the Webda json filter

Parameters

object: unknown

The object to export

Returns

string

The export of the strip object ( removed all attribute with _ )

Inherited from

Service.toPublicJSON

Source

packages/core/src/services/service.ts:552


toString()

toString(): string

Return service representation

Returns

string

Inherited from

Service.toString

Source

packages/core/src/services/service.ts:380


getEventListeners()

static getEventListeners(emitter, name): Function[]

Returns a copy of the array of listeners for the event named eventName.

For EventEmitters this behaves exactly the same as calling .listeners on the emitter.

For EventTargets this is the only way to get the event listeners for the event target. This is useful for debugging and diagnostic purposes.

const { getEventListeners, EventEmitter } = require('events');

{
const ee = new EventEmitter();
const listener = () => console.log('Events are fun');
ee.on('foo', listener);
getEventListeners(ee, 'foo'); // [listener]
}
{
const et = new EventTarget();
const listener = () => console.log('Events are fun');
et.addEventListener('foo', listener);
getEventListeners(et, 'foo'); // [listener]
}

Parameters

emitter: EventEmitter | _DOMEventTarget

name: string | symbol

Returns

Function[]

Inherited from

Service.getEventListeners

Since

v15.2.0, v14.17.0

Source

packages/core/node_modules/@types/node/events.d.ts:299


listenerCount()

static listenerCount(emitter, eventName): number

A class method that returns the number of listeners for the given eventNameregistered on the given emitter.

const { EventEmitter, listenerCount } = require('events');
const myEmitter = new EventEmitter();
myEmitter.on('event', () => {});
myEmitter.on('event', () => {});
console.log(listenerCount(myEmitter, 'event'));
// Prints: 2

Parameters

emitter: EventEmitter

The emitter to query

eventName: string | symbol

The event name

Returns

number

Inherited from

Service.listenerCount

Since

v0.9.12

Deprecated

Since v3.2.0 - Use listenerCount instead.

Source

packages/core/node_modules/@types/node/events.d.ts:271


on()

static on(emitter, eventName, options?): AsyncIterableIterator<any>

const { on, EventEmitter } = require('events');

(async () => {
const ee = new EventEmitter();

// Emit later on
process.nextTick(() => {
ee.emit('foo', 'bar');
ee.emit('foo', 42);
});

for await (const event of on(ee, 'foo')) {
// The execution of this inner block is synchronous and it
// processes one event at a time (even with await). Do not use
// if concurrent execution is required.
console.log(event); // prints ['bar'] [42]
}
// Unreachable here
})();

Returns an AsyncIterator that iterates eventName events. It will throw if the EventEmitter emits 'error'. It removes all listeners when exiting the loop. The value returned by each iteration is an array composed of the emitted event arguments.

An AbortSignal can be used to cancel waiting on events:

const { on, EventEmitter } = require('events');
const ac = new AbortController();

(async () => {
const ee = new EventEmitter();

// Emit later on
process.nextTick(() => {
ee.emit('foo', 'bar');
ee.emit('foo', 42);
});

for await (const event of on(ee, 'foo', { signal: ac.signal })) {
// The execution of this inner block is synchronous and it
// processes one event at a time (even with await). Do not use
// if concurrent execution is required.
console.log(event); // prints ['bar'] [42]
}
// Unreachable here
})();

process.nextTick(() => ac.abort());

Parameters

emitter: EventEmitter

eventName: string

The name of the event being listened for

options?: StaticEventEmitterOptions

Returns

AsyncIterableIterator<any>

that iterates eventName events emitted by the emitter

Inherited from

Service.on

Since

v13.6.0, v12.16.0

Source

packages/core/node_modules/@types/node/events.d.ts:254


once()

once(emitter, eventName, options)

static once(emitter, eventName, options?): Promise<any[]>

Creates a Promise that is fulfilled when the EventEmitter emits the given event or that is rejected if the EventEmitter emits 'error' while waiting. The Promise will resolve with an array of all the arguments emitted to the given event.

This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event semantics and does not listen to the 'error' event.

const { once, EventEmitter } = require('events');

async function run() {
const ee = new EventEmitter();

process.nextTick(() => {
ee.emit('myevent', 42);
});

const [value] = await once(ee, 'myevent');
console.log(value);

const err = new Error('kaboom');
process.nextTick(() => {
ee.emit('error', err);
});

try {
await once(ee, 'myevent');
} catch (err) {
console.log('error happened', err);
}
}

run();

The special handling of the 'error' event is only used when events.once()is used to wait for another event. If events.once() is used to wait for the 'error' event itself, then it is treated as any other kind of event without special handling:

const { EventEmitter, once } = require('events');

const ee = new EventEmitter();

once(ee, 'error')
.then(([err]) => console.log('ok', err.message))
.catch((err) => console.log('error', err.message));

ee.emit('error', new Error('boom'));

// Prints: ok boom

An AbortSignal can be used to cancel waiting for the event:

const { EventEmitter, once } = require('events');

const ee = new EventEmitter();
const ac = new AbortController();

async function foo(emitter, event, signal) {
try {
await once(emitter, event, { signal });
console.log('event emitted!');
} catch (error) {
if (error.name === 'AbortError') {
console.error('Waiting for the event was canceled!');
} else {
console.error('There was an error', error.message);
}
}
}

foo(ee, 'foo', ac.signal);
ac.abort(); // Abort waiting for the event
ee.emit('foo'); // Prints: Waiting for the event was canceled!
Parameters

emitter: _NodeEventTarget

eventName: string | symbol

options?: StaticEventEmitterOptions

Returns

Promise<any[]>

Inherited from

Service.once

Since

v11.13.0, v10.16.0

Source

packages/core/node_modules/@types/node/events.d.ts:194

once(emitter, eventName, options)

static once(emitter, eventName, options?): Promise<any[]>

Parameters

emitter: _DOMEventTarget

eventName: string

options?: StaticEventEmitterOptions

Returns

Promise<any[]>

Inherited from

Service.once

Source

packages/core/node_modules/@types/node/events.d.ts:195


setMaxListeners()

static setMaxListeners(n?, ...eventTargets?): void

const {
setMaxListeners,
EventEmitter
} = require('events');

const target = new EventTarget();
const emitter = new EventEmitter();

setMaxListeners(5, target, emitter);

Parameters

n?: number

A non-negative number. The maximum number of listeners per EventTarget event.

• ...eventTargets?: (EventEmitter | _DOMEventTarget)[]

Returns

void

Inherited from

Service.setMaxListeners

Since

v15.4.0

Source

packages/core/node_modules/@types/node/events.d.ts:317