ModuleClient class
IoT Hub device client used to connect a device with an Azure IoT hub.
Users of the SDK should call one of the factory methods, fromConnectionString or fromSharedAccessSignature to create an IoT Hub device client.
- Extends
-
InternalClient
Inherited Properties
capture |
Value: boolean Change the default |
capture |
Value: See how to write a custom |
default |
By default, a maximum of Take caution when setting the This is not a hard limit. The
The The emitted warning can be inspected with |
error |
This symbol shall be used to install a listener for only monitoring Installing a listener using this symbol does not change the behavior once an |
Methods
close() | |
close(Callback<Disconnected>) | Closes the transport connection and destroys the client resources. Note: After calling this method the ModuleClient object cannot be reused. |
from |
Creates an IoT Hub module client from the given authentication method and using the given transport type. |
from |
Creates an IoT Hub device client from the given connection string using the given transport type. |
from |
|
from |
Creates an IoT Hub module client by using configuration information from the environment. If an environment variable called
|
from |
Creates an IoT Hub module client from the given shared access signature using the given transport type. |
invoke |
|
invoke |
Invokes a method on a downstream device or on another module on the same IoTEdge device. Please note that this feature only works when the module is being run as part of an IoTEdge device. |
invoke |
|
invoke |
|
on |
Registers a callback for a method named |
send |
|
send |
Sends an event to the given module output |
send |
|
send |
Sends an array of events to the given module output |
set |
|
set |
Passes options to the |
Inherited Methods
abandon(Message) | |
abandon(Message, Callback<Message |
|
add |
Listens once to the Listening to the This API allows safely using Returns a disposable so that it may be unsubscribed from more easily.
|
add |
Alias for |
complete(Message) | |
complete(Message, Callback<Message |
|
emit<K>(string | symbol, Any |
Synchronously calls each of the listeners registered for the event named Returns
|
event |
Returns an array listing the events for which the emitter has registered
listeners. The values in the array are strings or
|
get |
Returns a copy of the array of listeners for the event named For For
|
get |
Returns the current max listener value for the |
get |
Returns the currently set max amount of listeners. For For
|
get |
|
get |
|
listener |
A class method that returns the number of listeners for the given
|
listener |
Returns the number of listeners listening for the event named |
listeners<K>(string | symbol) | Returns a copy of the array of listeners for the event named
|
off<K>(string | symbol, (args: any[]) => void) | Alias for |
on(Event |
Returns an An
Use the
|
on(Event |
|
on<K>(string | symbol, (args: any[]) => void) | Adds the
Returns a reference to the By default, event listeners are invoked in the order they are added. The
|
once(Event |
Creates a This method is intentionally generic and works with the web platform EventTarget interface, which has no special
The special handling of the
An
|
once(Event |
|
once<K>(string | symbol, (args: any[]) => void) | Adds a one-time
Returns a reference to the By default, event listeners are invoked in the order they are added. The
|
open() | |
open(Callback<Connected>) | |
prepend |
Adds the
Returns a reference to the |
prepend |
Adds a one-time
Returns a reference to the |
raw |
Returns a copy of the array of listeners for the event named
|
reject(Message) | |
reject(Message, Callback<Message |
|
remove |
Removes all listeners, or those of the specified It is bad practice to remove listeners added elsewhere in the code,
particularly when the Returns a reference to the |
remove |
Removes the specified
Once an event is emitted, all listeners attached to it at the
time of emitting are called in order. This implies that any
Because listeners are managed using an internal array, calling this will
change the position indices of any listener registered after the listener
being removed. This will not impact the order in which listeners are called,
but it means that any copies of the listener array as returned by
the When a single function has been added as a handler multiple times for a single
event (as in the example below),
Returns a reference to the |
send |
|
send |
|
send |
|
send |
|
set |
By default Returns a reference to the |
set |
|
set |
Sets the retry policy used by the client on all operations. The default is ExponentialBackoffWithJitter. |
set |
|
set |
|
update |
|
[capture |
Inherited Property Details
captureRejections
Value: boolean
Change the default captureRejections
option on all new EventEmitter
objects.
static captureRejections: boolean
Property Value
boolean
Inherited From InternalClient.captureRejections
captureRejectionSymbol
Value: Symbol.for('nodejs.rejection')
See how to write a custom rejection handler
.
static captureRejectionSymbol: typeof captureRejectionSymbol
Property Value
typeof captureRejectionSymbol
Inherited From InternalClient.captureRejectionSymbol
defaultMaxListeners
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'
.
static defaultMaxListeners: number
Property Value
number
Inherited From InternalClient.defaultMaxListeners
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.
static errorMonitor: typeof errorMonitor
Property Value
typeof errorMonitor
Inherited From InternalClient.errorMonitor
Method Details
close()
function close(): Promise<Disconnected>
Returns
Promise<Disconnected>
close(Callback<Disconnected>)
Closes the transport connection and destroys the client resources.
Note: After calling this method the ModuleClient object cannot be reused.
function close(closeCallback?: Callback<Disconnected>)
Parameters
- closeCallback
-
Callback<Disconnected>
Optional function to call once the transport is disconnected and the client closed.
fromAuthenticationProvider(AuthenticationProvider, any)
Creates an IoT Hub module client from the given authentication method and using the given transport type.
static function fromAuthenticationProvider(authenticationProvider: AuthenticationProvider, transportCtor: any): ModuleClient
Parameters
- authenticationProvider
-
AuthenticationProvider
Object used to obtain the authentication parameters for the IoT hub.
- transportCtor
-
any
Transport protocol used to connect to IoT hub.
Returns
fromConnectionString(string, any)
Creates an IoT Hub device client from the given connection string using the given transport type.
static function fromConnectionString(connStr: string, transportCtor: any): ModuleClient
Parameters
- connStr
-
string
A connection string which encapsulates "device connect" permissions on an IoT hub.
- transportCtor
-
any
A transport constructor.
Returns
fromEnvironment(any)
static function fromEnvironment(transportCtor: any): Promise<ModuleClient>
Parameters
- transportCtor
-
any
Returns
Promise<ModuleClient>
fromEnvironment(any, Callback<ModuleClient>)
Creates an IoT Hub module client by using configuration information from the environment.
If an environment variable called EdgeHubConnectionString
or IotHubConnectionString
exists, then that value is used and behavior is identical
to calling fromConnectionString
passing that in. If those environment variables do not exist then the following variables MUST be defined:
- IOTEDGE_WORKLOADURI URI for iotedged's workload API
- IOTEDGE_DEVICEID Device identifier
- IOTEDGE_MODULEID Module identifier
- IOTEDGE_MODULEGENERATIONID Module generation identifier
- IOTEDGE_IOTHUBHOSTNAME IoT Hub host name
- IOTEDGE_AUTHSCHEME Authentication scheme to use; must be "sasToken"
static function fromEnvironment(transportCtor: any, callback?: Callback<ModuleClient>)
Parameters
- transportCtor
-
any
Transport protocol used to connect to IoT hub.
- callback
-
Callback<ModuleClient>
Optional callback to invoke when the ModuleClient has been constructed or if an error occurs while creating the client.
fromSharedAccessSignature(string, any)
Creates an IoT Hub module client from the given shared access signature using the given transport type.
static function fromSharedAccessSignature(sharedAccessSignature: string, transportCtor: any): ModuleClient
Parameters
- sharedAccessSignature
-
string
A shared access signature which encapsulates "device connect" permissions on an IoT hub.
- transportCtor
-
any
Returns
invokeMethod(string, MethodParams)
function invokeMethod(deviceId: string, methodParams: MethodParams): Promise<MethodResult>
Parameters
- deviceId
-
string
- methodParams
-
MethodParams
Returns
Promise<MethodResult>
invokeMethod(string, MethodParams, Callback<MethodResult>)
Invokes a method on a downstream device or on another module on the same IoTEdge device. Please note that this feature only works when the module is being run as part of an IoTEdge device.
function invokeMethod(deviceId: string, methodParams: MethodParams, callback?: Callback<MethodResult>)
Parameters
- deviceId
-
string
target device identifier
- methodParams
-
MethodParams
parameters of the direct method call
- callback
-
Callback<MethodResult>
optional callback that will be invoked either with an Error object or the result of the method call.
invokeMethod(string, string, MethodParams)
function invokeMethod(deviceId: string, moduleId: string, methodParams: MethodParams): Promise<MethodResult>
Parameters
- deviceId
-
string
- moduleId
-
string
- methodParams
-
MethodParams
Returns
Promise<MethodResult>
invokeMethod(string, string, MethodParams, Callback<MethodResult>)
function invokeMethod(deviceId: string, moduleId: string, methodParams: MethodParams, callback: Callback<MethodResult>)
Parameters
- deviceId
-
string
- moduleId
-
string
- methodParams
-
MethodParams
- callback
-
Callback<MethodResult>
onMethod(string, DoubleValueCallback<DeviceMethodRequest, DeviceMethodResponse>)
Registers a callback for a method named methodName
.
function onMethod(methodName: string, callback: DoubleValueCallback<DeviceMethodRequest, DeviceMethodResponse>)
Parameters
- methodName
-
string
Name of the method that will be handled by the callback
- callback
-
DoubleValueCallback<DeviceMethodRequest, DeviceMethodResponse>
Function that shall be called whenever a method request for the method called methodName
is received.
sendOutputEvent(string, Message)
function sendOutputEvent(outputName: string, message: Message): Promise<MessageEnqueued>
Parameters
- outputName
-
string
- message
- Message
Returns
Promise<MessageEnqueued>
sendOutputEvent(string, Message, Callback<MessageEnqueued>)
Sends an event to the given module output
function sendOutputEvent(outputName: string, message: Message, callback?: Callback<MessageEnqueued>)
Parameters
- outputName
-
string
Name of the output to send the event to
- message
- Message
Message to send to the given output
- callback
-
Callback<MessageEnqueued>
Optional function to call when the operation has been queued.
sendOutputEventBatch(string, Message[])
function sendOutputEventBatch(outputName: string, messages: Message[]): Promise<MessageEnqueued>
Parameters
- outputName
-
string
- messages
-
Message[]
Returns
Promise<MessageEnqueued>
sendOutputEventBatch(string, Message[], Callback<MessageEnqueued>)
Sends an array of events to the given module output
function sendOutputEventBatch(outputName: string, messages: Message[], callback?: Callback<MessageEnqueued>)
Parameters
- outputName
-
string
Name of the output to send the events to
- messages
-
Message[]
- callback
-
Callback<MessageEnqueued>
Function to call when the operations have been queued.
setOptions(DeviceClientOptions)
function setOptions(options: DeviceClientOptions): Promise<TransportConfigured>
Parameters
- options
- DeviceClientOptions
Returns
Promise<TransportConfigured>
setOptions(DeviceClientOptions, Callback<TransportConfigured>)
Passes options to the ModuleClient
object that can be used to configure the transport.
function setOptions(options: DeviceClientOptions, done?: Callback<TransportConfigured>)
Parameters
- options
- DeviceClientOptions
A DeviceClientOptions object.
- done
-
Callback<TransportConfigured>
Optional callback to call once the options have been set.
Inherited Method Details
abandon(Message)
function abandon(message: Message): Promise<MessageAbandoned>
Parameters
- message
- Message
Returns
Promise<MessageAbandoned>
Inherited From InternalClient.abandon
abandon(Message, Callback<MessageAbandoned>)
function abandon(message: Message, abandonCallback: Callback<MessageAbandoned>)
Parameters
- message
- Message
- abandonCallback
-
Callback<MessageAbandoned>
Inherited From InternalClient.abandon
addAbortListener(AbortSignal, (event: Event) => void)
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 AbortSignal
s 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]();
}
}
static function addAbortListener(signal: AbortSignal, resource: (event: Event) => void): Disposable
Parameters
- signal
-
AbortSignal
- resource
-
(event: Event) => void
Returns
Disposable
Disposable that removes the abort
listener.
Inherited From InternalClient.addAbortListener
addListener<K>(string | symbol, (args: any[]) => void)
Alias for emitter.on(eventName, listener)
.
function addListener<K>(eventName: string | symbol, listener: (args: any[]) => void): ModuleClient
Parameters
- eventName
-
string | symbol
- listener
-
(args: any[]) => void
Returns
Inherited From InternalClient.addListener
complete(Message)
function complete(message: Message): Promise<MessageCompleted>
Parameters
- message
- Message
Returns
Promise<MessageCompleted>
Inherited From InternalClient.complete
complete(Message, Callback<MessageCompleted>)
function complete(message: Message, completeCallback: Callback<MessageCompleted>)
Parameters
- message
- Message
- completeCallback
-
Callback<MessageCompleted>
Inherited From InternalClient.complete
emit<K>(string | symbol, AnyRest)
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 listener
function emit<K>(eventName: string | symbol, args: AnyRest): boolean
Parameters
- eventName
-
string | symbol
- args
-
AnyRest
Returns
boolean
Inherited From InternalClient.emit
eventNames()
Returns an array listing the events for which the emitter has registered
listeners. The values in the array are strings or Symbol
s.
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) ]
function eventNames(): (string | symbol)[]
Returns
(string | symbol)[]
Inherited From InternalClient.eventNames
getEventListeners(EventEmitter<DefaultEventMap> | EventTarget, string | symbol)
Returns a copy of the array of listeners for the event named eventName
.
For EventEmitter
s this behaves exactly the same as calling .listeners
on
the emitter.
For EventTarget
s 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] ]
}
static function getEventListeners(emitter: EventEmitter<DefaultEventMap> | EventTarget, name: string | symbol): Function[]
Parameters
- emitter
-
EventEmitter<DefaultEventMap> | EventTarget
- name
-
string | symbol
Returns
Function[]
Inherited From InternalClient.getEventListeners
getMaxListeners()
Returns the current max listener value for the EventEmitter
which is either
set by emitter.setMaxListeners(n)
or defaults to defaultMaxListeners.
function getMaxListeners(): number
Returns
number
Inherited From InternalClient.getMaxListeners
getMaxListeners(EventEmitter<DefaultEventMap> | EventTarget)
Returns the currently set max amount of listeners.
For EventEmitter
s this behaves exactly the same as calling .getMaxListeners
on
the emitter.
For EventTarget
s 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
}
static function getMaxListeners(emitter: EventEmitter<DefaultEventMap> | EventTarget): number
Parameters
- emitter
-
EventEmitter<DefaultEventMap> | EventTarget
Returns
number
Inherited From InternalClient.getMaxListeners
getTwin()
getTwin(Callback<Twin>)
function getTwin(done: Callback<Twin>)
Parameters
- done
-
Callback<Twin>
Inherited From InternalClient.getTwin
listenerCount(EventEmitter<DefaultEventMap>, string | symbol)
Warning
This API is now deprecated.
Since v3.2.0 - Use listenerCount
instead.
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
static function listenerCount(emitter: EventEmitter<DefaultEventMap>, eventName: string | symbol): number
Parameters
- emitter
-
EventEmitter<DefaultEventMap>
The emitter to query
- eventName
-
string | symbol
The event name
Returns
number
Inherited From InternalClient.listenerCount
listenerCount<K>(string | symbol, Function)
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.
function listenerCount<K>(eventName: string | symbol, listener?: Function): number
Parameters
- eventName
-
string | symbol
The name of the event being listened for
- listener
-
Function
The event handler function
Returns
number
Inherited From InternalClient.listenerCount
listeners<K>(string | symbol)
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] ]
function listeners<K>(eventName: string | symbol): Function[]
Parameters
- eventName
-
string | symbol
Returns
Function[]
Inherited From InternalClient.listeners
off<K>(string | symbol, (args: any[]) => void)
Alias for emitter.removeListener()
.
function off<K>(eventName: string | symbol, listener: (args: any[]) => void): ModuleClient
Parameters
- eventName
-
string | symbol
- listener
-
(args: any[]) => void
Returns
Inherited From InternalClient.off
on(EventEmitter<DefaultEventMap>, string | symbol, StaticEventEmitterIteratorOptions)
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'
static function on(emitter: EventEmitter<DefaultEventMap>, eventName: string | symbol, options?: StaticEventEmitterIteratorOptions): AsyncIterator<any[], any, any>
Parameters
- emitter
-
EventEmitter<DefaultEventMap>
- eventName
-
string | symbol
- options
-
StaticEventEmitterIteratorOptions
Returns
AsyncIterator<any[], any, any>
An AsyncIterator
that iterates eventName
events emitted by the emitter
Inherited From InternalClient.on
on(EventTarget, string, StaticEventEmitterIteratorOptions)
static function on(emitter: EventTarget, eventName: string, options?: StaticEventEmitterIteratorOptions): AsyncIterator<any[], any, any>
Parameters
- emitter
-
EventTarget
- eventName
-
string
- options
-
StaticEventEmitterIteratorOptions
Returns
AsyncIterator<any[], any, any>
Inherited From InternalClient.on
on<K>(string | symbol, (args: any[]) => void)
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
// a
function on<K>(eventName: string | symbol, listener: (args: any[]) => void): ModuleClient
Parameters
- eventName
-
string | symbol
The name of the event.
- listener
-
(args: any[]) => void
The callback function
Returns
Inherited From InternalClient.on
once(EventEmitter<DefaultEventMap>, string | symbol, StaticEventEmitterOptions)
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!
static function once(emitter: EventEmitter<DefaultEventMap>, eventName: string | symbol, options?: StaticEventEmitterOptions): Promise<any[]>
Parameters
- emitter
-
EventEmitter<DefaultEventMap>
- eventName
-
string | symbol
- options
-
StaticEventEmitterOptions
Returns
Promise<any[]>
Inherited From InternalClient.once
once(EventTarget, string, StaticEventEmitterOptions)
static function once(emitter: EventTarget, eventName: string, options?: StaticEventEmitterOptions): Promise<any[]>
Parameters
- emitter
-
EventTarget
- eventName
-
string
- options
-
StaticEventEmitterOptions
Returns
Promise<any[]>
Inherited From InternalClient.once
once<K>(string | symbol, (args: any[]) => void)
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
// a
function once<K>(eventName: string | symbol, listener: (args: any[]) => void): ModuleClient
Parameters
- eventName
-
string | symbol
The name of the event.
- listener
-
(args: any[]) => void
The callback function
Returns
Inherited From InternalClient.once
open()
function open(): Promise<Connected>
Returns
Promise<Connected>
Inherited From InternalClient.open
open(Callback<Connected>)
function open(openCallback: Callback<Connected>)
Parameters
- openCallback
-
Callback<Connected>
Inherited From InternalClient.open
prependListener<K>(string | symbol, (args: any[]) => void)
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.
function prependListener<K>(eventName: string | symbol, listener: (args: any[]) => void): ModuleClient
Parameters
- eventName
-
string | symbol
The name of the event.
- listener
-
(args: any[]) => void
The callback function
Returns
Inherited From InternalClient.prependListener
prependOnceListener<K>(string | symbol, (args: any[]) => void)
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.
function prependOnceListener<K>(eventName: string | symbol, listener: (args: any[]) => void): ModuleClient
Parameters
- eventName
-
string | symbol
The name of the event.
- listener
-
(args: any[]) => void
The callback function
Returns
Inherited From InternalClient.prependOnceListener
rawListeners<K>(string | symbol)
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');
function rawListeners<K>(eventName: string | symbol): Function[]
Parameters
- eventName
-
string | symbol
Returns
Function[]
Inherited From InternalClient.rawListeners
reject(Message)
function reject(message: Message): Promise<MessageRejected>
Parameters
- message
- Message
Returns
Promise<MessageRejected>
Inherited From InternalClient.reject
reject(Message, Callback<MessageRejected>)
function reject(message: Message, rejectCallback: Callback<MessageRejected>)
Parameters
- message
- Message
- rejectCallback
-
Callback<MessageRejected>
Inherited From InternalClient.reject
removeAllListeners(string | symbol)
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.
function removeAllListeners(eventName?: string | symbol): ModuleClient
Parameters
- eventName
-
string | symbol
Returns
Inherited From InternalClient.removeAllListeners
removeListener<K>(string | symbol, (args: any[]) => void)
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:
// A
Because listeners are managed using an internal array, calling this will
change the position indices of any listener registered after the listener
being removed. This will not impact the order in which listeners are called,
but it means that any copies of the listener array as returned by
the emitter.listeners()
method will need to be recreated.
When a single function has been added as a handler multiple times for a single
event (as in the example below), removeListener()
will remove the most
recently added instance. In the example the once('ping')
listener is removed:
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.
function removeListener<K>(eventName: string | symbol, listener: (args: any[]) => void): ModuleClient
Parameters
- eventName
-
string | symbol
- listener
-
(args: any[]) => void
Returns
Inherited From InternalClient.removeListener
sendEvent(Message)
function sendEvent(message: Message): Promise<MessageEnqueued>
Parameters
- message
- Message
Returns
Promise<MessageEnqueued>
Inherited From InternalClient.sendEvent
sendEvent(Message, Callback<MessageEnqueued>)
function sendEvent(message: Message, sendEventCallback: Callback<MessageEnqueued>)
Parameters
- message
- Message
- sendEventCallback
-
Callback<MessageEnqueued>
Inherited From InternalClient.sendEvent
sendEventBatch(Message[])
function sendEventBatch(messages: Message[]): Promise<MessageEnqueued>
Parameters
- messages
-
Message[]
Returns
Promise<MessageEnqueued>
Inherited From InternalClient.sendEventBatch
sendEventBatch(Message[], Callback<MessageEnqueued>)
function sendEventBatch(messages: Message[], sendEventBatchCallback: Callback<MessageEnqueued>)
Parameters
- messages
-
Message[]
- sendEventBatchCallback
-
Callback<MessageEnqueued>
Inherited From InternalClient.sendEventBatch
setMaxListeners(number)
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.
function setMaxListeners(n: number): ModuleClient
Parameters
- n
-
number
Returns
Inherited From InternalClient.setMaxListeners
setMaxListeners(number, (EventEmitter<DefaultEventMap> | EventTarget)[])
import { setMaxListeners, EventEmitter } from 'node:events';
const target = new EventTarget();
const emitter = new EventEmitter();
setMaxListeners(5, target, emitter);
static function setMaxListeners(n?: number, eventTargets: (EventEmitter<DefaultEventMap> | EventTarget)[])
Parameters
- 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 {EventEmitter}
objects.
Inherited From InternalClient.setMaxListeners
setRetryPolicy(RetryPolicy)
Sets the retry policy used by the client on all operations. The default is ExponentialBackoffWithJitter.
function setRetryPolicy(policy: RetryPolicy)
Parameters
- policy
-
RetryPolicy
{RetryPolicy} The retry policy that should be used for all future operations.
Inherited From InternalClient.setRetryPolicy
setTransportOptions(any)
function setTransportOptions(options: any): Promise<TransportConfigured>
Parameters
- options
-
any
Returns
Promise<TransportConfigured>
Inherited From InternalClient.setTransportOptions
setTransportOptions(any, Callback<TransportConfigured>)
function setTransportOptions(options: any, done: Callback<TransportConfigured>)
Parameters
- options
-
any
- done
-
Callback<TransportConfigured>
Inherited From InternalClient.setTransportOptions
updateSharedAccessSignature(string, Callback<SharedAccessSignatureUpdated>)
function updateSharedAccessSignature(sharedAccessSignature: string, updateSasCallback?: Callback<SharedAccessSignatureUpdated>)
Parameters
- sharedAccessSignature
-
string
- updateSasCallback
-
Callback<SharedAccessSignatureUpdated>
Inherited From InternalClient.updateSharedAccessSignature
[captureRejectionSymbol]<K>(Error, string | symbol, AnyRest)
function [captureRejectionSymbol]<K>(error: Error, event: string | symbol, args: AnyRest)
Parameters
- error
-
Error
- event
-
string | symbol
- args
-
AnyRest
Inherited From InternalClient.__@captureRejectionSymbol@141