Class: Client

Extends: EventEmitter

Main class for working with Yurba API

The Client class is the main entry point for interacting with the Yurba.one platform. It provides methods for sending messages, registering commands, handling events, and managing bot functionality.

Examples

import { Client } from 'yurba.js';

const client = new Client();

client.commands.register('hello', { name: 'string' }, (message, args) => {
  message.reply(`Hello, ${args.name}!`);
});

client.on('ready', () => {
  console.log('Bot is ready!');
});

client.init('your-token-here');

const client = new Client({
  prefix: '!',
  maxReconnectAttempts: 10
});

Constructors

Constructor

new Client(options): Client

Create a Client

Parameters

Name	Type	Description
options?	ClientOptions	Client configuration options

Returns

Client

Example

const client = new Client({
  prefix: '!',
  maxReconnectAttempts: 10,
  intents: ['dialogs']
});

Overrides

EventEmitter.constructor

Properties

api

readonly api: REST

---

commands

readonly commands: CommandManager

The command manager of this client

---

prefix

prefix: string = '/'

---

userClient

readonly userClient: UserClientManager

The user client manager of this client

---

users

readonly users: UserManager

The user manager of this client

---

captureRejections

static captureRejections: boolean

Value: boolean

Change the default captureRejections option on all new EventEmitter objects.

Inherited from

EventEmitter.captureRejections

---

captureRejectionSymbol

readonly static captureRejectionSymbol: typeof captureRejectionSymbol

Value: Symbol.for('nodejs.rejection')

See how to write a custom rejection handler.

Inherited from

EventEmitter.captureRejectionSymbol

---

defaultMaxListeners

static defaultMaxListeners: number

By default, a maximum of 10 listeners can be registered for any single event. This limit can be changed for individual EventEmitter instances using the emitter.setMaxListeners(n) method. To change the default for allEventEmitter instances, the events.defaultMaxListeners property can be used. If this value is not a positive number, a RangeError is thrown.

Take caution when setting the events.defaultMaxListeners because the change affects all EventEmitter instances, including those created before the change is made. However, calling emitter.setMaxListeners(n) still has precedence over events.defaultMaxListeners.

This is not a hard limit. The EventEmitter instance will allow more listeners to be added but will output a trace warning to stderr indicating that a "possible EventEmitter memory leak" has been detected. For any single EventEmitter, the emitter.getMaxListeners() and emitter.setMaxListeners() methods can be used to temporarily avoid this warning:

import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.setMaxListeners(emitter.getMaxListeners() + 1);
emitter.once('event', () => {
  // do stuff
  emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));
});

The --trace-warnings command-line flag can be used to display the stack trace for such warnings.

The emitted warning can be inspected with process.on('warning') and will have the additional emitter, type, and count properties, referring to the event emitter instance, the event's name and the number of attached listeners, respectively. Its name property is set to 'MaxListenersExceededWarning'.

Inherited from

EventEmitter.defaultMaxListeners

---

errorMonitor

readonly static 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

EventEmitter.errorMonitor

Accessors

dialogs

Get Signature

get dialogs(): undefined | DialogModel[]

Getter for bot user dialogs

Returns

undefined | DialogModel[]

Dialogs

---

readyAt

Get Signature

get readyAt(): null | Date

Timestamp when the client became ready

Returns

null | Date

---

uptime

Get Signature

get uptime(): null | number

Duration in milliseconds since the client became ready

Returns

null | number

---

user

Get Signature

get user(): null | UserModel

Gets bot user data (synchronous)

Returns

null | UserModel

User | null Bot user data or null if loading

Methods

[captureRejectionSymbol]()?

optional [captureRejectionSymbol]<K>(error, event, ...args): void

Type Parameters

Name	Type	Description
K	any

Parameters

Name	Type	Description
error	Error
event	string | symbol
args	AnyRest

Returns

void

Inherited from

EventEmitter.[captureRejectionSymbol]

---

addListener()

addListener<K>(eventName, listener): this

Alias for emitter.on(eventName, listener).

Type Parameters

Name	Type	Description
K	any

Parameters

Name	Type	Description
eventName	string | symbol
listener	(...args) => void

Returns

this

Inherited from

EventEmitter.addListener

---

deleteMessage(ID): Promise<boolean>

`

Deletes a message by its ID

Parameters

Name	Type	Description
ID	number	Message ID to delete

Returns

Promise<boolean>

Promise that resolves with boolean indicating success

---

emit(event, ...args): `boolean``

**`Internal`**

Emits the specified event with given arguments

Parameters

Name	Type	Description
event	string | symbol	Event name or symbol
args	unknown[]	Arguments to pass to event listeners

Returns

boolean *? True if the event had listeners, false otherwise

Example

client.emit('customEvent', { foo: 'bar' });

Overrides

EventEmitter.emit

---

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.

import { EventEmitter } from 'node: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

EventEmitter.eventNames

---

getMaxListeners()

getMaxListeners(): number

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

Returns

number

Inherited from

EventEmitter.getMaxListeners

---

getMiddlewares()

getMiddlewares(): MiddlewareConfig[]

Gets a list of all middleware

Returns

MiddlewareConfig[]

Array of middleware configurations

Throws

If middleware manager is not initialized

---

getPhoto(photoId): Promise<null | Photo>

`

Gets a photo from Yurba

Parameters

Name	Type	Description
photoId	string	Photo ID to retrieve

Returns

Promise<null | Photo>

Promise that resolves with API response

---

init(token): Promise<void>

`

Initializes the client

Parameters

Name	Type	Description
token?	undefined | string | boolean

Returns

Promise<void>

Promise that resolves after successful initialization

Throws

Thrown if the token is missing or invalid. Possible error codes:

• ErrorCodes.TokenMissing
• ErrorCodes.TokenInvalid

---

listenerCount()

listenerCount<K>(eventName, listener?): number

Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

Type Parameters

Name	Type	Description
K	any

Parameters

Name	Type	Description
eventName	string | symbol	The name of the event being listened for
listener?	Function	The event handler function

Returns

number

Inherited from

EventEmitter.listenerCount

---

listeners()

listeners<K>(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] ]

Type Parameters

Name	Type	Description
K	any

Parameters

Name	Type	Description
eventName	string | symbol

Returns

Function[]

Inherited from

EventEmitter.listeners

---

off(event, listener): this

`

Removes a listener for the specified event

Parameters

Name	Type	Description
event	string | symbol	Event name or symbol
listener	(...args) => void	Callback function to remove

Returns

this *? Client instance

Example

const handler = (msg) => {};
client.on('message', handler);
client.off('message', handler);

Overrides

EventEmitter.off

---

on(event, listener): this

`

Adds a listener for the specified event

Parameters

Name	Type	Description
event	string | symbol	Event name or symbol
listener	(...args) => void	Callback function

Returns

this *? Client instance

Example

client.on('message', (msg) => {
  console.log('Received message:', msg);
});

Overrides

EventEmitter.on

---

once(event, listener): this

`

Adds a one-time listener for the specified event

The listener is invoked only the next time the event is triggered, then removed

Parameters

Name	Type	Description
event	string | symbol	Event name or symbol
listener	(...args) => void	Callback function

Returns

this *? Client instance

Example

client.once('ready', () => {
  console.log('Bot is ready!');
});

Overrides

EventEmitter.once

---

prependListener()

prependListener<K>(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 eventName and 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.

Type Parameters

Name	Type	Description
K	any

Parameters

Name	Type	Description
eventName	string | symbol	The name of the event.
listener	(...args) => void	The callback function

Returns

this

Inherited from

EventEmitter.prependListener

---

prependOnceListener()

prependOnceListener<K>(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.

Type Parameters

Name	Type	Description
K	any

Parameters

Name	Type	Description
eventName	string | symbol	The name of the event.
listener	(...args) => void	The callback function

Returns

this

Inherited from

EventEmitter.prependOnceListener

---

rawListeners()

rawListeners<K>(eventName): Function[]

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

import { EventEmitter } from 'node:events';
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');

Type Parameters

Name	Type	Description
K	any

Parameters

Name	Type	Description
eventName	string | symbol

Returns

Function[]

Inherited from

EventEmitter.rawListeners

---

removeAllListeners(event?): this

`

Removes all listeners or those specified for an event

Parameters

Name	Type	Description
event?	string | symbol	Event name or symbol (optional)

Returns

this *? Client instance

Example

client.removeAllListeners('message');

Overrides

EventEmitter.removeAllListeners

---

removeListener(event, listener): this

`

Removes a specific listener from an event

Alias for off()

Parameters

Name	Type	Description
event	string | symbol	Event name or symbol
listener	(...args) => void	Callback function to remove

Returns

this *? Client instance

Overrides

EventEmitter.removeListener

---

removeMiddleware(name): boolean

`

Removes middleware by name

Parameters

Name	Type	Description
name	string	Middleware name

Returns

boolean *? Boolean indicating whether the middleware was removed

Throws

If middleware manager is not initialized

---

sendMessage(dialogId, payload): Promise<MessageModel>

`

Send message to dialog

Parameters

Name	Type	Description
dialogId	number	Dialog identifier
payload	SendMessagePayload	SendMessagePayload Message data

Returns

Promise<MessageModel>

Message Sent message

Example

// Text message
await client.sendMessage(123, { text: "Hello!" });

// With photos and reply
await client.sendMessage(123, {
  text: "Check this",
  photos_list: [-1112],
  replyTo: 48561
});

// With attachments
await client.sendMessage(123, {
  text: "Media",
  attachments: [
    { Type: "video", Item: 28 },
    { Type: "track", Item: 6422 },
    { Type: "file", Item: 684 },
    { Type: "post", Item: 3201 }
  ]
});

// Edit message
await client.sendMessage(123, {
  text: "Updated",
  edit: 12345
});

---

setMaxListeners(n): this v0.3.5

By default `EventEmitter`s 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 to Infinity (or 0) to indicate an unlimited number of listeners.

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

Parameters

Name	Type	Description
n	number

Returns

this

Inherited from

EventEmitter.setMaxListeners

---

typing(dialogId): void

`

Shows typing indicator in dialog

Parameters

Name	Type	Description
dialogId	number	Dialog ID

Returns

void

Throws

If WebSocket manager is not initialized or connection is closed

---

use(middleware, config?): void

`

Adds a middleware function to execute for each incoming message

Parameters

Name	Type	Description
middleware	MiddlewareFunction	Middleware function
config?	MiddlewareConfig	Middleware configuration

Returns

void

Throws

If middleware manager is not initialized

---

waitFor()

waitFor<T>(event, check, options): Promise<unknown>

Waits for a specific event and resolves when the check function returns true

Type Parameters

Name	Type	Description
T	unknown[]	Type of arguments passed to the event

Parameters

Name	Type	Description
event	string	Event name to listen for
check	(...args) => boolean	Function that receives event arguments and returns boolean,

         indicating whether the desired condition is met |

| options? | object | Additional parameters:

• timeout: Maximum time to wait for the event in milliseconds. Default is 60000.
• multiple: If true, resolves with all arguments as an array; otherwise resolves with the first argument or full array of arguments if there are multiple.
• signal: AbortSignal to cancel the wait operation. |

Returns

Promise<unknown>

Promise that resolves with event arguments when condition is met, or rejects if timeout is reached or operation is cancelled.

Examples

1
// Wait for a message with text "Hello"
await client.waitFor('message', msg => msg.Text === 'Hello', { timeout: 5000 });

2
// Wait for user event and get all arguments
const [arg1, arg2] = await client.waitFor('customEvent', () => true, { multiple: true });

---

addAbortListener()

static addAbortListener(signal, resource): Disposable

Listens once to the abort event on the provided signal.

Listening to the abort event on abort signals is unsafe and may lead to resource leaks since another third party with the signal can call e.stopImmediatePropagation(). Unfortunately Node.js cannot change this since it would violate the web standard. Additionally, the original API makes it easy to forget to remove listeners.

This API allows safely using AbortSignals in Node.js APIs by solving these two issues by listening to the event such that stopImmediatePropagation does not prevent the listener from running.

Returns a disposable so that it may be unsubscribed from more easily.

import { addAbortListener } from 'node:events';

function example(signal) {
  let disposable;
  try {
    signal.addEventListener('abort', (e) => e.stopImmediatePropagation());
    disposable = addAbortListener(signal, (e) => {
      // Do something when signal is aborted.
    });
  } finally {
    disposable?.[Symbol.dispose]();
  }
}

Parameters

Name	Type	Description
signal	AbortSignal
resource	(event) => void

Returns

Disposable *? Disposable that removes the abort listener.

Inherited from

EventEmitter.addAbortListener

---

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.

import { getEventListeners, EventEmitter } from 'node:events';

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

Parameters

Name	Type	Description
emitter	EventEmitter<DefaultEventMap> | EventTarget
name	string | symbol

Returns

Function[]

Inherited from

EventEmitter.getEventListeners

---

getMaxListeners()

static getMaxListeners(emitter): number

Returns the currently set max amount of listeners.

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

For EventTargets this is the only way to get the max event listeners for the event target. If the number of event handlers on a single EventTarget exceeds the max set, the EventTarget will print a warning.

import { getMaxListeners, setMaxListeners, EventEmitter } from 'node:events';

{
  const ee = new EventEmitter();
  console.log(getMaxListeners(ee)); // 10
  setMaxListeners(11, ee);
  console.log(getMaxListeners(ee)); // 11
}
{
  const et = new EventTarget();
  console.log(getMaxListeners(et)); // 10
  setMaxListeners(11, et);
  console.log(getMaxListeners(et)); // 11
}

Parameters

Name	Type	Description
emitter	EventEmitter<DefaultEventMap> | EventTarget

Returns

number

Inherited from

EventEmitter.getMaxListeners

---

listenerCount()

static listenerCount(emitter, eventName): number

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

import { EventEmitter, listenerCount } from 'node:events';

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

Parameters

Name	Type	Description
emitter	EventEmitter	The emitter to query
eventName	string | symbol	The event name

Returns

number

Deprecated

Since v3.2.0 - Use listenerCount instead.

Inherited from

EventEmitter.listenerCount

---

on()

Call Signature

static on(emitter, eventName, options?): AsyncIterator<any[]>

import { on, EventEmitter } from 'node:events';
import process from 'node:process';

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:

import { on, EventEmitter } from 'node:events';
import process from 'node:process';

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());

Use the close option to specify an array of event names that will end the iteration:

import { on, EventEmitter } from 'node:events';
import process from 'node:process';

const ee = new EventEmitter();

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

for await (const event of on(ee, 'foo', { close: ['close'] })) {
  console.log(event); // prints ['bar'] [42]
}
// the loop will exit after 'close' is emitted
console.log('done'); // prints 'done'

Parameters

Name	Type	Description
emitter	EventEmitter
eventName	string | symbol
options?	StaticEventEmitterIteratorOptions

Returns

AsyncIterator<any[]>

An AsyncIterator that iterates eventName events emitted by the emitter

Inherited from

EventEmitter.on

Call Signature

static on(emitter, eventName, options?): AsyncIterator<any[]>

import { on, EventEmitter } from 'node:events';
import process from 'node:process';

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:

import { on, EventEmitter } from 'node:events';
import process from 'node:process';

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());

Use the close option to specify an array of event names that will end the iteration:

import { on, EventEmitter } from 'node:events';
import process from 'node:process';

const ee = new EventEmitter();

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

for await (const event of on(ee, 'foo', { close: ['close'] })) {
  console.log(event); // prints ['bar'] [42]
}
// the loop will exit after 'close' is emitted
console.log('done'); // prints 'done'

Parameters

Name	Type	Description
emitter	EventTarget
eventName	string
options?	StaticEventEmitterIteratorOptions

Returns

AsyncIterator<any[]>

An AsyncIterator that iterates eventName events emitted by the emitter

Inherited from

EventEmitter.on

---

once()

Call Signature

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.

import { once, EventEmitter } from 'node:events';
import process from 'node:process';

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.error('error happened', err);
}

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:

import { EventEmitter, once } from 'node:events';

const ee = new EventEmitter();

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

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

// Prints: ok boom

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

import { EventEmitter, once } from 'node: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

Name	Type	Description
emitter	EventEmitter
eventName	string | symbol
options?	StaticEventEmitterOptions

Returns

Promise<any[]>

Inherited from

EventEmitter.once

Call Signature

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.

import { once, EventEmitter } from 'node:events';
import process from 'node:process';

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.error('error happened', err);
}

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:

import { EventEmitter, once } from 'node:events';

const ee = new EventEmitter();

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

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

// Prints: ok boom

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

import { EventEmitter, once } from 'node: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

Name	Type	Description
emitter	EventTarget
eventName	string
options?	StaticEventEmitterOptions

Returns

Promise<any[]>

Inherited from

EventEmitter.once

---

setMaxListeners()

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

import { setMaxListeners, EventEmitter } from 'node:events';

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

setMaxListeners(5, target, emitter);

Parameters

Name	Type	Description
n?	number	A non-negative number. The maximum number of listeners per EventTarget event.
eventTargets	(EventEmitter<DefaultEventMap> | EventTarget)[]	Zero or more {EventTarget} or {EventEmitter} instances. If none are specified, n is set as the default max for all newly created {EventTarget} and
objects.

Returns

void

Inherited from

EventEmitter.setMaxListeners