Class: fs.StatWatcher
interface
fs.StatWatcher
interface StatWatcher
- eventName: string | symbol,listener: (...args: any[]) => void): this;
Alias for
emitter.on(eventName, listener)
. - eventName: string | symbol,...args: AnyRest): 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 listener
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) ]
Returns the current max listener value for the
EventEmitter
which is either set byemitter.setMaxListeners(n)
or defaults to EventEmitter.defaultMaxListeners.- eventName: string | symbol,listener?: Function): number;
Returns the number of listeners listening for the event named
eventName
. Iflistener
is provided, it will return how many times the listener is found in the list of the listeners of the event.@param eventNameThe name of the event being listened for
@param listenerThe event handler function
- eventName: string | symbol): 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] ]
- eventName: string | symbol,listener: (...args: any[]) => void): this;
Alias for
emitter.removeListener()
. - eventName: string | symbol,listener: (...args: any[]) => void): this;
Adds the
listener
function to the end of the listeners array for the event namedeventName
. No checks are made to see if thelistener
has already been added. Multiple calls passing the same combination ofeventName
andlistener
will result in thelistener
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
@param eventNameThe name of the event.
@param listenerThe callback function
- eventName: string | symbol,listener: (...args: any[]) => void): this;
Adds a one-time
listener
function for the event namedeventName
. The next timeeventName
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
@param eventNameThe name of the event.
@param listenerThe callback function
- eventName: string | symbol,listener: (...args: any[]) => void): this;
Adds the
listener
function to the beginning of the listeners array for the event namedeventName
. No checks are made to see if thelistener
has already been added. Multiple calls passing the same combination ofeventName
andlistener
will result in thelistener
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.@param eventNameThe name of the event.
@param listenerThe callback function
- eventName: string | symbol,listener: (...args: any[]) => void): this;
Adds a one-time
listener
function for the event namedeventName
to the beginning of the listeners array. The next timeeventName
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.@param eventNameThe name of the event.
@param listenerThe callback function
- eventName: string | symbol): 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');
When called, requests that the Node.js event loop not exit so long as the
fs.StatWatcher
is active. Callingwatcher.ref()
multiple times will have no effect.By default, all
fs.StatWatcher
objects are "ref'ed", making it normally unnecessary to callwatcher.ref()
unlesswatcher.unref()
had been called previously.- eventName?: string | symbol): 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. - eventName: string | symbol,listener: (...args: any[]) => void): this;
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);
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 specifiedeventName
, thenremoveListener()
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()
orremoveAllListeners()
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 theonce('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. - n: number): this;
By default
EventEmitter
s will print a warning if more than10
listeners are added for a particular event. This is a useful default that helps finding memory leaks. Theemitter.setMaxListeners()
method allows the limit to be modified for this specificEventEmitter
instance. The value can be set toInfinity
(or0
) to indicate an unlimited number of listeners.Returns a reference to the
EventEmitter
, so that calls can be chained. When called, the active
fs.StatWatcher
object will not require the Node.js event loop to remain active. If there is no other activity keeping the event loop running, the process may exit before thefs.StatWatcher
object's callback is invoked. Callingwatcher.unref()
multiple times will have no effect.