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@webda/core • Readme | API

Class: ConfigurationService<T, E>

Handle sessionSecret ( rolling between two secrets ) expire every hour Handle longTermSecret ( rolling between two longer secret ) expire every month

Load configuration from another service

If the result contains webda.services in his object then webda configuration will be dynamically reloaded

Webda Modda​

Extends​

Type parameters​

• T extends ConfigurationServiceParameters = ConfigurationServiceParameters

• E extends ConfigurationEvents = ConfigurationEvents

Constructors​

new ConfigurationService(webda, name, params)​

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

ConfigurationService<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

_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

_webda​

protected _webda: Core<CoreEvents>

Webda Core object

Inherited from​

Service._webda

Source​

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

configuration​

protected configuration: any

Current configuration

Source​

packages/core/src/services/configuration.ts:91

logger​

protected logger: Logger

Logger with class context

Inherited from​

Service.logger

Source​

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

metrics?​

protected metrics?: any

Get metrics

Inherited from​

Service.metrics

Source​

packages/core/src/services/service.ts:325

nextCheck​

protected nextCheck: number

Source​

packages/core/src/services/configuration.ts:71

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

serializedConfiguration​

protected serializedConfiguration: any

Source​

packages/core/src/services/configuration.ts:67

sourceId​

protected sourceId: string

Source id to retrieve

Source​

packages/core/src/services/configuration.ts:79

sourceService​

protected sourceService: ConfigurationProvider

Service that will provide the information

Source​

packages/core/src/services/configuration.ts:75

watchs​

protected watchs: any[] = []

Watchs for configuration update

Source​

packages/core/src/services/configuration.ts:87

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

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

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

checkUpdate()​

protected checkUpdate(dynamic): Promise<void>

Checking for configuration updates

If configuration is updated, it will trigger all the watchs accordingly

Parameters​

• dynamic: boolean= false

Returns​

Promise<void>

Source​

packages/core/src/services/configuration.ts:200

computeParameters()​

computeParameters(): void

Used to compute or derivate input parameter to attribute

Returns​

void

Inherited from​

Service.computeParameters

Source​

packages/core/src/services/service.ts:352

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

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

getConfiguration()​

getConfiguration(): any

Returns​

any

current configuration

Source​

packages/core/src/services/configuration.ts:167

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

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

Return the full path url based on parameters

Parameters​

• url: string

relative url to service

• _methods: HttpMethodType[]

in case we need filtering (like Store)

Returns​

string

absolute url or undefined if need to skip the Route

Inherited from​

Service.getUrl

Source​

packages/core/src/services/service.ts:449

getWebda()​

getWebda(): Core<CoreEvents>

Return WebdaCore

Returns​

Core<CoreEvents>

Inherited from​

Service.getWebda

Source​

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

init()​

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

Will be called after all the Services are created

Returns​

Promise<ConfigurationService<T, E>>

Overrides​

Service.init

Abstract​

Source​

packages/core/src/services/configuration.ts:106

initConfiguration()​

initConfiguration(): Promise<Object>

Returns​

Promise<Object>

Source​

packages/core/src/services/configuration.ts:189

initMetrics()​

initMetrics(): void

Init the metrics

Returns​

void

Inherited from​

Service.initMetrics

Source​

packages/core/src/services/service.ts:404

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

loadAndStoreConfiguration()​

loadAndStoreConfiguration(): Promise<Object>

Read the file and store it

Returns​

Promise<Object>

Source​

packages/core/src/services/configuration.ts:252

loadConfiguration()​

protected loadConfiguration(): Promise<Object>

Load the configuration by calling the source service with the source id

Returns​

Promise<Object>

Source​

packages/core/src/services/configuration.ts:185

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

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

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

reinit()​

reinit(_config): Promise<ConfigurationService<T, E>>

Parameters​

• _config: any

new parameters for the service

Returns​

Promise<ConfigurationService<T, E>>

Overrides​

Service.reinit

Source​

packages/core/src/services/configuration.ts:176

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

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>

Clear the check interval if exist

Returns​

Promise<void>

Overrides​

Service.stop

Source​

packages/core/src/services/configuration.ts:155

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

updateNextCheck()​

protected updateNextCheck(): void

Update the next check time

Returns​

void

Source​

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

watch()​

watch(jsonPath, callback, defaultValue): void

Watch a specific configuration modification

Parameters​

• jsonPath: string

JSON Path to the object to watch

• callback: (update) => void | Promise<void>

Method to call with the updated version

• defaultValue: any= undefined

Default value of the jsonPath if it does not exist

Returns​

void

Source​

packages/core/src/services/configuration.ts:148

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