ServerCapabilities
Defined in: src/serverCapabilities.ts:74
Manages storing and periodically refreshing the server capabilities.
Extends
Section titled “Extends”CapabilityPoller<Capabilities>
Constructors
Section titled “Constructors”Constructor
Section titled “Constructor”new ServerCapabilities(
logger,http):ServerCapabilities
Defined in: src/serverCapabilities.ts:75
Parameters
Section titled “Parameters”logger
Section titled “logger”Logger
DigitalWorldHttpApi<IHttpOpts & object>
Returns
Section titled “Returns”ServerCapabilities
Overrides
Section titled “Overrides”CapabilityPoller<Capabilities>.constructor
Properties
Section titled “Properties”captureRejections
Section titled “captureRejections”
staticcaptureRejections:boolean
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:425
Value: boolean
Change the default captureRejections option on all new EventEmitter objects.
v13.4.0, v12.16.0
Inherited from
Section titled “Inherited from”CapabilityPoller.captureRejections
captureRejectionSymbol
Section titled “captureRejectionSymbol”
readonlystaticcaptureRejectionSymbol: typeofcaptureRejectionSymbol
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:418
Value: Symbol.for('nodejs.rejection')
See how to write a custom rejection handler.
v13.4.0, v12.16.0
Inherited from
Section titled “Inherited from”CapabilityPoller.captureRejectionSymbol
defaultMaxListeners
Section titled “defaultMaxListeners”
staticdefaultMaxListeners:number
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:464
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'.
v0.11.2
Inherited from
Section titled “Inherited from”CapabilityPoller.defaultMaxListeners
errorMonitor
Section titled “errorMonitor”
readonlystaticerrorMonitor: typeoferrorMonitor
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:411
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.
v13.6.0, v12.17.0
Inherited from
Section titled “Inherited from”CapabilityPoller.errorMonitor
Methods
Section titled “Methods”[captureRejectionSymbol]()?
Section titled “[captureRejectionSymbol]()?”
optional[captureRejectionSymbol]<K>(error,event, …args):void
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:103
Type Parameters
Section titled “Type Parameters”K
Parameters
Section titled “Parameters”Error
string | symbol
…AnyRest
Returns
Section titled “Returns”void
Inherited from
Section titled “Inherited from”CapabilityPoller.[captureRejectionSymbol]
addListener()
Section titled “addListener()”addListener<
T>(event,listener):this
Defined in: src/models/typed-event-emitter.ts:70
Alias for on.
Type Parameters
Section titled “Type Parameters”T extends EventEmitterEvents | "update"
Parameters
Section titled “Parameters”T
listener
Section titled “listener”Listener<"update", { update: (data) => void; }, T>
Returns
Section titled “Returns”this
Inherited from
Section titled “Inherited from”CapabilityPoller.addListener
emit()
Section titled “emit()”Call Signature
Section titled “Call Signature”emit<
T>(event, …args):boolean
Defined in: src/models/typed-event-emitter.ts:86
Synchronously calls each of the listeners registered for the event named
event, in the order they were registered, passing the supplied arguments
to each.
Type Parameters
Section titled “Type Parameters”T extends "update"
Parameters
Section titled “Parameters”T
The name of the event to emit
…Parameters<object[T]>
Arguments to pass to the listener
Returns
Section titled “Returns”boolean
true if the event had listeners, false otherwise.
Inherited from
Section titled “Inherited from”CapabilityPoller.emit
Call Signature
Section titled “Call Signature”emit<
T>(event, …args):boolean
Defined in: src/models/typed-event-emitter.ts:87
Synchronously calls each of the listeners registered for the event named
event, in the order they were registered, passing the supplied arguments
to each.
Type Parameters
Section titled “Type Parameters”T extends "update"
Parameters
Section titled “Parameters”T
The name of the event to emit
…Parameters<object[T]>
Arguments to pass to the listener
Returns
Section titled “Returns”boolean
true if the event had listeners, false otherwise.
Inherited from
Section titled “Inherited from”CapabilityPoller.emit
emitPromised()
Section titled “emitPromised()”Call Signature
Section titled “Call Signature”emitPromised<
T>(event, …args):Promise<boolean>
Defined in: src/models/typed-event-emitter.ts:98
Similar to emit but calls all listeners within a Promise.all and returns the promise chain
Type Parameters
Section titled “Type Parameters”T extends "update"
Parameters
Section titled “Parameters”T
The name of the event to emit
…Parameters<object[T]>
Arguments to pass to the listener
Returns
Section titled “Returns”Promise<boolean>
true if the event had listeners, false otherwise.
Inherited from
Section titled “Inherited from”CapabilityPoller.emitPromised
Call Signature
Section titled “Call Signature”emitPromised<
T>(event, …args):Promise<boolean>
Defined in: src/models/typed-event-emitter.ts:102
Similar to emit but calls all listeners within a Promise.all and returns the promise chain
Type Parameters
Section titled “Type Parameters”T extends "update"
Parameters
Section titled “Parameters”T
The name of the event to emit
…Parameters<object[T]>
Arguments to pass to the listener
Returns
Section titled “Returns”Promise<boolean>
true if the event had listeners, false otherwise.
Inherited from
Section titled “Inherited from”CapabilityPoller.emitPromised
eventNames()
Section titled “eventNames()”eventNames(): (
string|symbol)[]
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:967
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
Section titled “Returns”(string | symbol)[]
v6.0.0
Inherited from
Section titled “Inherited from”CapabilityPoller.eventNames
fetch()
Section titled “fetch()”fetch():
Promise<Capabilities>
Defined in: src/serverCapabilities.ts:82
Fetches the latest server capabilities from the hub and returns them, or rejects on failure.
Returns
Section titled “Returns”Promise<Capabilities>
Overrides
Section titled “Overrides”CapabilityPoller.fetch
getCached()
Section titled “getCached()”getCached():
Capabilities|undefined
Defined in: src/capabilityPoller.ts:67
Returns the cached capabilities, or undefined if none are cached.
Returns
Section titled “Returns”Capabilities | undefined
the current capabilities, if any.
Inherited from
Section titled “Inherited from”CapabilityPoller.getCached
getMaxListeners()
Section titled “getMaxListeners()”getMaxListeners():
number
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:819
Returns the current max listener value for the EventEmitter which is either
set by emitter.setMaxListeners(n) or defaults to EventEmitter.defaultMaxListeners.
Returns
Section titled “Returns”number
v1.0.0
Inherited from
Section titled “Inherited from”CapabilityPoller.getMaxListeners
listenerCount()
Section titled “listenerCount()”listenerCount(
event):number
Defined in: src/models/typed-event-emitter.ts:115
Returns the number of listeners listening to the event named event.
Parameters
Section titled “Parameters”EventEmitterEvents | "update"
The name of the event being listened for
Returns
Section titled “Returns”number
Inherited from
Section titled “Inherited from”CapabilityPoller.listenerCount
listeners()
Section titled “listeners()”listeners(
event):Function[]
Defined in: src/models/typed-event-emitter.ts:122
Returns a copy of the array of listeners for the event named event.
Parameters
Section titled “Parameters”EventEmitterEvents | "update"
Returns
Section titled “Returns”Function[]
Inherited from
Section titled “Inherited from”CapabilityPoller.listeners
off<
T>(event,listener):this
Defined in: src/models/typed-event-emitter.ts:129
Alias for removeListener
Type Parameters
Section titled “Type Parameters”T extends EventEmitterEvents | "update"
Parameters
Section titled “Parameters”T
listener
Section titled “listener”Listener<"update", { update: (data) => void; }, T>
Returns
Section titled “Returns”this
Inherited from
Section titled “Inherited from”CapabilityPoller.off
on<
T>(event,listener):this
Defined in: src/models/typed-event-emitter.ts:150
Adds the listener function to the end of the listeners array for the
event named event.
No checks are made to see if the listener has already been added. Multiple calls
passing the same combination of event and listener will result in the listener
being added, and called, multiple times.
By default, event listeners are invoked in the order they are added. The prependListener method can be used as an alternative to add the event listener to the beginning of the listeners array.
Type Parameters
Section titled “Type Parameters”T extends EventEmitterEvents | "update"
Parameters
Section titled “Parameters”T
The name of the event.
listener
Section titled “listener”Listener<"update", { update: (data) => void; }, T>
The callback function
Returns
Section titled “Returns”this
a reference to the EventEmitter, so that calls can be chained.
Inherited from
Section titled “Inherited from”CapabilityPoller.on
once()
Section titled “once()”once<
T>(event,listener):this
Defined in: src/models/typed-event-emitter.ts:169
Adds a one-time listener function for the event named event. The
next time event is triggered, this listener is removed and then invoked.
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 prependOnceListener method can be used as an alternative to add the event listener to the beginning of the listeners array.
Type Parameters
Section titled “Type Parameters”T extends EventEmitterEvents | "update"
Parameters
Section titled “Parameters”T
The name of the event.
listener
Section titled “listener”Listener<"update", { update: (data) => void; }, T>
The callback function
Returns
Section titled “Returns”this
a reference to the EventEmitter, so that calls can be chained.
Inherited from
Section titled “Inherited from”CapabilityPoller.once
prependListener()
Section titled “prependListener()”prependListener<
T>(event,listener):this
Defined in: src/models/typed-event-emitter.ts:186
Adds the listener function to the beginning of the listeners array for the
event named event.
No checks are made to see if the listener has already been added. Multiple calls
passing the same combination of event and listener will result in the listener
being added, and called, multiple times.
Type Parameters
Section titled “Type Parameters”T extends EventEmitterEvents | "update"
Parameters
Section titled “Parameters”T
The name of the event.
listener
Section titled “listener”Listener<"update", { update: (data) => void; }, T>
The callback function
Returns
Section titled “Returns”this
a reference to the EventEmitter, so that calls can be chained.
Inherited from
Section titled “Inherited from”CapabilityPoller.prependListener
prependOnceListener()
Section titled “prependOnceListener()”prependOnceListener<
T>(event,listener):this
Defined in: src/models/typed-event-emitter.ts:202
Adds a one-timelistener function for the event named event to the beginning of the listeners array.
The next time event is triggered, this listener is removed, and then invoked.
Type Parameters
Section titled “Type Parameters”T extends EventEmitterEvents | "update"
Parameters
Section titled “Parameters”T
The name of the event.
listener
Section titled “listener”Listener<"update", { update: (data) => void; }, T>
The callback function
Returns
Section titled “Returns”this
a reference to the EventEmitter, so that calls can be chained.
Inherited from
Section titled “Inherited from”CapabilityPoller.prependOnceListener
rawListeners()
Section titled “rawListeners()”rawListeners(
event):Function[]
Defined in: src/models/typed-event-emitter.ts:243
Returns a copy of the array of listeners for the event named eventName,
including any wrappers (such as those created by .once()).
Parameters
Section titled “Parameters”EventEmitterEvents | "update"
Returns
Section titled “Returns”Function[]
Inherited from
Section titled “Inherited from”CapabilityPoller.rawListeners
removeAllListeners()
Section titled “removeAllListeners()”removeAllListeners(
event?):this
Defined in: src/models/typed-event-emitter.ts:219
Removes all listeners, or those of the specified event.
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).
Parameters
Section titled “Parameters”event?
Section titled “event?”EventEmitterEvents | "update"
The name of the event. If undefined, all listeners everywhere are removed.
Returns
Section titled “Returns”this
a reference to the EventEmitter, so that calls can be chained.
Inherited from
Section titled “Inherited from”CapabilityPoller.removeAllListeners
removeListener()
Section titled “removeListener()”removeListener<
T>(event,listener):this
Defined in: src/models/typed-event-emitter.ts:232
Removes the specified listener from the listener array for the event named event.
Type Parameters
Section titled “Type Parameters”T extends EventEmitterEvents | "update"
Parameters
Section titled “Parameters”T
listener
Section titled “listener”Listener<"update", { update: (data) => void; }, T>
Returns
Section titled “Returns”this
a reference to the EventEmitter, so that calls can be chained.
Inherited from
Section titled “Inherited from”CapabilityPoller.removeListener
setMaxListeners()
Section titled “setMaxListeners()”setMaxListeners(
n):this
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:813
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
Section titled “Parameters”number
Returns
Section titled “Returns”this
v0.3.5
Inherited from
Section titled “Inherited from”CapabilityPoller.setMaxListeners
start()
Section titled “start()”start():
void
Defined in: src/capabilityPoller.ts:52
Starts periodically fetching the server capabilities.
Returns
Section titled “Returns”void
Inherited from
Section titled “Inherited from”CapabilityPoller.start
stop()
Section titled “stop()”stop():
void
Defined in: src/capabilityPoller.ts:59
Stops the service
Returns
Section titled “Returns”void
Inherited from
Section titled “Inherited from”CapabilityPoller.stop
addAbortListener()
Section titled “addAbortListener()”
staticaddAbortListener(signal,resource):Disposable
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:403
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
Section titled “Parameters”signal
Section titled “signal”AbortSignal
resource
Section titled “resource”(event) => void
Returns
Section titled “Returns”Disposable
Disposable that removes the abort listener.
v20.5.0
Inherited from
Section titled “Inherited from”CapabilityPoller.addAbortListener
getEventListeners()
Section titled “getEventListeners()”
staticgetEventListeners(emitter,name):Function[]
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:325
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
Section titled “Parameters”emitter
Section titled “emitter”EventEmitter<DefaultEventMap> | EventTarget
string | symbol
Returns
Section titled “Returns”Function[]
v15.2.0, v14.17.0
Inherited from
Section titled “Inherited from”CapabilityPoller.getEventListeners
getMaxListeners()
Section titled “getMaxListeners()”
staticgetMaxListeners(emitter):number
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:354
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
Section titled “Parameters”emitter
Section titled “emitter”EventEmitter<DefaultEventMap> | EventTarget
Returns
Section titled “Returns”number
v19.9.0
Inherited from
Section titled “Inherited from”CapabilityPoller.getMaxListeners
listenerCount()
Section titled “listenerCount()”
staticlistenerCount(emitter,eventName):number
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:297
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
Section titled “Parameters”emitter
Section titled “emitter”EventEmitter
The emitter to query
eventName
Section titled “eventName”string | symbol
The event name
Returns
Section titled “Returns”number
v0.9.12
Inherited from
Section titled “Inherited from”CapabilityPoller.listenerCount
Call Signature
Section titled “Call Signature”
staticon(emitter,eventName,options?):AsyncIterator<any[]>
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:270
import { on, EventEmitter } from 'node:events';import process from 'node:process';
const ee = new EventEmitter();
// Emit later onprocess.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 onprocess.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 emittedconsole.log('done'); // prints 'done'Parameters
Section titled “Parameters”emitter
Section titled “emitter”EventEmitter
eventName
Section titled “eventName”string | symbol
options?
Section titled “options?”StaticEventEmitterIteratorOptions
Returns
Section titled “Returns”AsyncIterator<any[]>
An AsyncIterator that iterates eventName events emitted by the emitter
v13.6.0, v12.16.0
Inherited from
Section titled “Inherited from”CapabilityPoller.on
Call Signature
Section titled “Call Signature”
staticon(emitter,eventName,options?):AsyncIterator<any[]>
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:275
import { on, EventEmitter } from 'node:events';import process from 'node:process';
const ee = new EventEmitter();
// Emit later onprocess.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 onprocess.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 emittedconsole.log('done'); // prints 'done'Parameters
Section titled “Parameters”emitter
Section titled “emitter”EventTarget
eventName
Section titled “eventName”string
options?
Section titled “options?”StaticEventEmitterIteratorOptions
Returns
Section titled “Returns”AsyncIterator<any[]>
An AsyncIterator that iterates eventName events emitted by the emitter
v13.6.0, v12.16.0
Inherited from
Section titled “Inherited from”CapabilityPoller.on
once()
Section titled “once()”Call Signature
Section titled “Call Signature”
staticonce(emitter,eventName,options?):Promise<any[]>
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:184
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 eventee.emit('foo'); // Prints: Waiting for the event was canceled!Parameters
Section titled “Parameters”emitter
Section titled “emitter”EventEmitter
eventName
Section titled “eventName”string | symbol
options?
Section titled “options?”StaticEventEmitterOptions
Returns
Section titled “Returns”Promise<any[]>
v11.13.0, v10.16.0
Inherited from
Section titled “Inherited from”CapabilityPoller.once
Call Signature
Section titled “Call Signature”
staticonce(emitter,eventName,options?):Promise<any[]>
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:189
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 eventee.emit('foo'); // Prints: Waiting for the event was canceled!Parameters
Section titled “Parameters”emitter
Section titled “emitter”EventTarget
eventName
Section titled “eventName”string
options?
Section titled “options?”StaticEventEmitterOptions
Returns
Section titled “Returns”Promise<any[]>
v11.13.0, v10.16.0
Inherited from
Section titled “Inherited from”CapabilityPoller.once
setMaxListeners()
Section titled “setMaxListeners()”
staticsetMaxListeners(n?, …eventTargets):void
Defined in: node_modules/.pnpm/@types+node@22.20.0/node_modules/@types/node/events.d.ts:369
import { setMaxListeners, EventEmitter } from 'node:events';
const target = new EventTarget();const emitter = new EventEmitter();
setMaxListeners(5, target, emitter);Parameters
Section titled “Parameters”number
A non-negative number. The maximum number of listeners per EventTarget event.
eventTargets
Section titled “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 {EventEmitter}
objects.
Returns
Section titled “Returns”void
v15.4.0
Inherited from
Section titled “Inherited from”CapabilityPoller.setMaxListeners