Class: REST
Main REST client with lazy-loaded API resources
Extends
BaseClient
Constructors
Constructor
new REST(
options?):REST
Parameters
options?
Returns
REST
Overrides
BaseClient.constructor
Properties
captureRejections
staticcaptureRejections:boolean
Value: boolean
Change the default captureRejections option on all new EventEmitter objects.
Since
v13.4.0, v12.16.0
Inherited from
BaseClient.captureRejections
captureRejectionSymbol
readonlystaticcaptureRejectionSymbol: typeofcaptureRejectionSymbol
Value: Symbol.for('nodejs.rejection')
See how to write a custom rejection handler.
Since
v13.4.0, v12.16.0
Inherited from
BaseClient.captureRejectionSymbol
defaultMaxListeners
staticdefaultMaxListeners: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'.
Since
v0.11.2
Inherited from
BaseClient.defaultMaxListeners
errorMonitor
readonlystaticerrorMonitor: typeoferrorMonitor
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.
Since
v13.6.0, v12.17.0
Inherited from
BaseClient.errorMonitor
Accessors
account
Get Signature
get account():
AccountResource
Returns
apps
Get Signature
get apps():
AppResource
Returns
dialogs
Get Signature
get dialogs():
DialogResource
Returns
files
Get Signature
get files():
FilesResource
Returns
musebase
Get Signature
get musebase():
MusebaseResource
Returns
photos
Get Signature
get photos():
PhotosResource
Returns
posts
Get Signature
get posts():
PostResource
Returns
search
Get Signature
get search():
SearchResource
Returns
shop
Get Signature
get shop():
ShopResource
Returns
ShopResource
users
Get Signature
get users():
UserResource
Returns
video
Get Signature
get video():
VideoResource
Returns
Methods
[captureRejectionSymbol]()?
optional[captureRejectionSymbol]<K>(error,event, ...args):void
Type Parameters
K
K
Parameters
error
Error
event
string | symbol
args
...AnyRest
Returns
void
Inherited from
BaseClient.[captureRejectionSymbol]
addListener()
addListener<
K>(eventName,listener):this
Alias for emitter.on(eventName, listener).
Type Parameters
K
K
Parameters
eventName
string | symbol
listener
(...args) => void
Returns
this
Since
v0.1.26
Inherited from
BaseClient.addListener
batch()
batch():
BatchRequest
Create a new batch request for parallel API calls
Returns
BatchRequest instance
Example
const results = await rest.batch()
.add('user', rest.users.me())
.add('posts', rest.posts.get('@me', {}))
.execute();
console.log(results.user); // User object
console.log(results.posts); // Posts arraycancelAllRequests()
cancelAllRequests():
void
Returns
void
Inherited from
BaseClient.cancelAllRequests
cancelRequest()
cancelRequest(
endpoint):void
Parameters
endpoint
string
Returns
void
Inherited from
BaseClient.cancelRequest
clearCache()
clearCache():
void
Returns
void
Inherited from
BaseClient.clearCache
delete()
delete<
T>(endpoint,config?):Promise<T>
Type Parameters
T
T = unknown
Parameters
endpoint
string
config?
Returns
Promise<T>
Inherited from
BaseClient.delete
emit()
emit<
K>(eventName, ...args):boolean
Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each.
Returns true if the event had listeners, false otherwise.
import { EventEmitter } from 'node:events';
const myEmitter = new EventEmitter();
// First listener
myEmitter.on('event', function firstListener() {
console.log('Helloooo! first listener');
});
// Second listener
myEmitter.on('event', function secondListener(arg1, arg2) {
console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
});
// Third listener
myEmitter.on('event', function thirdListener(...args) {
const parameters = args.join(', ');
console.log(`event with parameters ${parameters} in third listener`);
});
console.log(myEmitter.listeners('event'));
myEmitter.emit('event', 1, 2, 3, 4, 5);
// Prints:
// [
// [Function: firstListener],
// [Function: secondListener],
// [Function: thirdListener]
// ]
// Helloooo! first listener
// event with parameters 1, 2 in second listener
// event with parameters 1, 2, 3, 4, 5 in third listenerType Parameters
K
K
Parameters
eventName
string | symbol
args
...AnyRest
Returns
boolean
Since
v0.1.26
Inherited from
BaseClient.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)[]
Since
v6.0.0
Inherited from
BaseClient.eventNames
get()
get<
T>(endpoint,queryParams?,config?):Promise<T>
Type Parameters
T
T = unknown
Parameters
endpoint
string
queryParams?
Record<string, unknown>
config?
Returns
Promise<T>
Inherited from
BaseClient.get
getCachedUser()
getCachedUser():
Promise<null|CachedUser>
Returns
Promise<null | CachedUser>
Inherited from
BaseClient.getCachedUser
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
Since
v1.0.0
Inherited from
BaseClient.getMaxListeners
getRateLimitStatus()
getRateLimitStatus():
null| {canMakeRequest:boolean;resetTime:number; }
Returns
null | { canMakeRequest: boolean; resetTime: number; }
Inherited from
BaseClient.getRateLimitStatus
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
K
K
Parameters
eventName
The name of the event being listened for
string | symbol
listener?
Function
The event handler function
Returns
number
Since
v3.2.0
Inherited from
BaseClient.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
K
K
Parameters
eventName
string | symbol
Returns
Function[]
Since
v0.1.26
Inherited from
BaseClient.listeners
off()
off<
K>(eventName,listener):this
Alias for emitter.removeListener().
Type Parameters
K
K
Parameters
eventName
string | symbol
listener
(...args) => void
Returns
this
Since
v10.0.0
Inherited from
BaseClient.off
on()
on<
K>(eventName,listener):this
Adds the listener function to the end 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.on('connection', (stream) => {
console.log('someone connected!');
});Returns a reference to the EventEmitter, so that calls can be chained.
By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.
import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// aType Parameters
K
K
Parameters
eventName
The name of the event.
string | symbol
listener
(...args) => void
The callback function
Returns
this
Since
v0.1.101
Inherited from
BaseClient.on
once()
once<
K>(eventName,listener):this
Adds a one-time listener 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. The emitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.
import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// aType Parameters
K
K
Parameters
eventName
The name of the event.
string | symbol
listener
(...args) => void
The callback function
Returns
this
Since
v0.3.0
Inherited from
BaseClient.once
patch()
patch<
T>(endpoint,data?,config?):Promise<T>
Type Parameters
T
T = unknown
Parameters
endpoint
string
data?
unknown
config?
Returns
Promise<T>
Inherited from
BaseClient.patch
post()
post<
T>(endpoint,data?,config?):Promise<T>
Type Parameters
T
T = unknown
Parameters
endpoint
string
data?
unknown
config?
Returns
Promise<T>
Inherited from
BaseClient.post
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
K
K
Parameters
eventName
The name of the event.
string | symbol
listener
(...args) => void
The callback function
Returns
this
Since
v6.0.0
Inherited from
BaseClient.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
K
K
Parameters
eventName
The name of the event.
string | symbol
listener
(...args) => void
The callback function
Returns
this
Since
v6.0.0
Inherited from
BaseClient.prependOnceListener
put()
put<
T>(endpoint,data?,config?):Promise<T>
Type Parameters
T
T = unknown
Parameters
endpoint
string
data?
unknown
config?
Returns
Promise<T>
Inherited from
BaseClient.put
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
K
K
Parameters
eventName
string | symbol
Returns
Function[]
Since
v9.4.0
Inherited from
BaseClient.rawListeners
removeAllListeners()
removeAllListeners(
eventName?):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
eventName?
string | symbol
Returns
this
Since
v0.1.26
Inherited from
BaseClient.removeAllListeners
removeListener()
removeListener<
K>(eventName,listener):this
Removes the specified listener from the listener array for the event named eventName.
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 any removeListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them fromemit() in progress. Subsequent events behave as expected.
import { EventEmitter } from 'node:events';
class MyEmitter extends EventEmitter {}
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:
// ABecause 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:
import { EventEmitter } from 'node:events';
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.
Type Parameters
K
K
Parameters
eventName
string | symbol
listener
(...args) => void
Returns
this
Since
v0.1.26
Inherited from
BaseClient.removeListener
resolveUser()
resolveUser(
user):Promise<string|number>
Parameters
user
string | number
Returns
Promise<string | number>
Inherited from
BaseClient.resolveUser
setCachedUser()
setCachedUser(
user):void
Parameters
user
Omit<CachedUser, "timestamp">
Returns
void
Inherited from
BaseClient.setCachedUser
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 to Infinity (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
Since
v0.3.5
Inherited from
BaseClient.setMaxListeners
setRateLimit()
setRateLimit(
config):void
Parameters
config
Returns
void
Inherited from
BaseClient.setRateLimit
setToken()
setToken(
token):this
Parameters
token
string
Returns
this
Inherited from
BaseClient.setToken
uploadFile()
uploadFile<
T>(endpoint,formData,config?):Promise<T>
Type Parameters
T
T = unknown
Parameters
endpoint
string
formData
FormData
config?
Returns
Promise<T>
Inherited from
BaseClient.uploadFile
addAbortListener()
staticaddAbortListener(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
signal
AbortSignal
resource
(event) => void
Returns
Disposable
Disposable that removes the abort listener.
Since
v20.5.0
Inherited from
BaseClient.addAbortListener
getEventListeners()
staticgetEventListeners(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
emitter
EventTarget | EventEmitter<DefaultEventMap>
name
string | symbol
Returns
Function[]
Since
v15.2.0, v14.17.0
Inherited from
BaseClient.getEventListeners
getMaxListeners()
staticgetMaxListeners(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
emitter
EventTarget | EventEmitter<DefaultEventMap>
Returns
number
Since
v19.9.0
Inherited from
BaseClient.getMaxListeners
listenerCount()
staticlistenerCount(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: 2Parameters
emitter
EventEmitter
The emitter to query
eventName
The event name
string | symbol
Returns
number
Since
v0.9.12
Deprecated
Since v3.2.0 - Use listenerCount instead.
Inherited from
BaseClient.listenerCount
on()
Call Signature
staticon(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 hereReturns 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
emitter
EventEmitter
eventName
string | symbol
options?
StaticEventEmitterIteratorOptions
Returns
AsyncIterator<any[]>
An AsyncIterator that iterates eventName events emitted by the emitter
Since
v13.6.0, v12.16.0
Inherited from
BaseClient.on
Call Signature
staticon(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 hereReturns 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
emitter
EventTarget
eventName
string
options?
StaticEventEmitterIteratorOptions
Returns
AsyncIterator<any[]>
An AsyncIterator that iterates eventName events emitted by the emitter
Since
v13.6.0, v12.16.0
Inherited from
BaseClient.on
once()
Call Signature
staticonce(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 boomAn 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
emitter
EventEmitter
eventName
string | symbol
options?
StaticEventEmitterOptions
Returns
Promise<any[]>
Since
v11.13.0, v10.16.0
Inherited from
BaseClient.once
Call Signature
staticonce(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 boomAn 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
emitter
EventTarget
eventName
string
options?
StaticEventEmitterOptions
Returns
Promise<any[]>
Since
v11.13.0, v10.16.0
Inherited from
BaseClient.once
setMaxListeners()
staticsetMaxListeners(n?, ...eventTargets?):void
import { setMaxListeners, EventEmitter } from 'node: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?
...(EventTarget | EventEmitter<DefaultEventMap>)[]
Zero or more {EventTarget} or {EventEmitter} instances. If none are specified, n is set as the default max for all newly created {EventTarget} and {EventEmitter} objects.
Returns
void
Since
v15.4.0
Inherited from
BaseClient.setMaxListeners