Internal Type of worker.
-Type of data sent to the worker. This can only be structured-cloneable data.
-Readonly clearClears tasks queue.
-Readonly closeCloses communication channel.
-Readonly deleteDeletes task function worker usage statistics.
-The task function name.
+InternalWorker node interface.
+Type of worker.
+Type of data sent to the worker. This can only be structured-cloneable data.
+ReadonlyclearClears tasks queue.
+ReadonlydeleteDeletes task function worker usage statistics.
+The task function name.
true if the task function worker usage statistics were deleted, false otherwise.
Readonly dequeueReadonly enqueueEnqueue task.
-The task to queue.
+ReadonlydequeueDequeue last prioritized task.
+ReadonlydequeueDequeue task.
+ReadonlyenqueueEnqueue task.
+Readonly getGets task function worker usage statistics.
-The task function name.
+ReadonlygetGets task function worker usage statistics.
+The task function name.
The task function worker usage statistics if the task function worker usage statistics are initialized, undefined otherwise.
Readonly hasWhether the worker node has back pressure (i.e. its tasks queue is full).
-true if the worker node has back pressure, false otherwise.
Readonly infoWorker info.
-Optional Readonly messageMessage channel (worker_threads only).
-Readonly popReadonly resetResets usage statistics.
-Optional strategyWorker choice strategy data. +
ReadonlyhasWhether the worker node has back pressure (i.e. its tasks queue is full).
+true if the worker node has back pressure, false otherwise.
ReadonlyinfoWorker info.
+Optional ReadonlymessageMessage channel (worker thread only).
+ReadonlyregisterRegisters once a worker event handler.
+The event.
+The event handler.
+ReadonlyregisterRegisters a worker event handler.
+The event.
+The event handler.
+ReadonlysetSets tasks queue priority.
+Whether to enable tasks queue priority.
+OptionalstrategyWorker choice strategy data. This is used to store data that are specific to the worker choice strategy.
-Tasks queue back pressure size. +
Tasks queue back pressure size. This is the number of tasks that can be enqueued before the worker node has back pressure.
-Readonly tasksTasks queue size.
-The tasks queue size.
-Readonly unshiftPrepends a task to the tasks queue.
-The task to prepend.
-The tasks queue size.
-Readonly usageWorker usage statistics.
-Readonly workerWorker.
-Optional [captureAlias for emitter.on(eventName, listener).
Rest ...args: any[]v0.1.26
-ReadonlytasksTasks queue size.
+The tasks queue size.
+ReadonlyterminateTerminates the worker node.
+ReadonlyusageWorker usage statistics.
+ReadonlyworkerWorker.
+Optional[captureRest...args: AnyRestAlias for emitter.on(eventName, listener).
Rest...args: any[]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
-Rest ...args: any[]v0.1.26
-Returns an array listing the events for which the emitter has registered +
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
+Rest...args: AnyRestReturns 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) ]
-v6.0.0
-Returns the current max listener value for the EventEmitter which is either
+
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 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.
The name of the event being listened for
-Optional listener: FunctionThe event handler function
-v3.2.0
-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] ]
-v0.1.26
-Alias for emitter.removeListener().
Rest ...args: any[]v10.0.0
-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 eventNameand listener will result in the listener being added, and called, multiple
-times.
server.on('connection', (stream) => {
console.log('someone connected!');
});
-The name of the event being listened for
+Optionallistener: FunctionThe event handler 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] ]
+Alias for emitter.removeListener().
Rest...args: any[]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. Theemitter.prependListener() method can be used as an alternative to add the
+
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
-The name of the event.
-The callback function
-Rest ...args: any[]v0.1.101
-Adds a one-timelistener function for the event named eventName. The
+
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
+The name of the event.
+The callback function
+Rest...args: any[]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!');
});
-server.once('connection', (stream) => {
console.log('Ah, we have our first user!');
});
+Returns a reference to the EventEmitter, so that calls can be chained.
By default, event listeners are invoked in the order they are added. Theemitter.prependOnceListener() method can be used as an alternative to add the
+
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
-The name of the event.
-The callback function
-Rest ...args: any[]v0.3.0
-Adds the listener function to the beginning of the listeners array for the
+
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
+The name of the event.
+The callback function
+Rest...args: any[]Adds the listener function to the beginning of the listeners array for the
event named eventName. No checks are made to see if the listener has
-already been added. Multiple calls passing the same combination of eventNameand listener will result in the listener being added, and called, multiple
-times.
server.prependListener('connection', (stream) => {
console.log('someone connected!');
});
-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.
The name of the event.
-The callback function
-Rest ...args: any[]v6.0.0
-Adds a one-timelistener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this
+
The name of the event.
+The callback function
+Rest...args: any[]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!');
});
-server.prependOnceListener('connection', (stream) => {
console.log('Ah, we have our first user!');
});
+Returns a reference to the EventEmitter, so that calls can be chained.
The name of the event.
-The callback function
-Rest ...args: any[]v6.0.0
-Returns a copy of the array of listeners for the event named eventName,
+
The name of the event.
+The callback function
+Rest...args: any[]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');
-v9.4.0
-Removes all listeners, or those of the specified eventName.
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');
+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.
Optional event: string | symbolv0.1.26
-Removes the specified listener from the listener array for the event namedeventName.
const callback = (stream) => {
console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);
-OptionaleventName: string | symbolRemoves 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 anyremoveListener() or removeAllListeners() calls after emitting and before the last listener finishes execution
+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
-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,
@@ -167,15 +188,16 @@ 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');
-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.
Rest ...args: any[]v0.1.26
-By default EventEmitters will print a warning if more than 10 listeners are
+
Rest...args: any[]By default EventEmitters will print a warning if more than 10 listeners are
added for a particular event. This is a useful default that helps finding
memory leaks. The emitter.setMaxListeners() method allows the limit to be
-modified for this specific EventEmitter instance. The value can be set toInfinity (or 0) to indicate an unlimited number of listeners.
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.
v0.3.5
-Generated using TypeDoc
Worker node interface.
-