dots.node.fs.fs-watcher — io.github.dots-cljs/dots-node 20.12.12-9

add-listener cljs

(add-listener fs-watcher event listener)

events.EventEmitter

1. change
2. close
3. error

Parameters:

• event: "error"
• listener: (error: Error) => void

Returns: FSWatcher

close cljs

(close fs-watcher)

Stop watching for changes on the given fs.FSWatcher. Once stopped, the fs.FSWatcher object is no longer usable.

Returns: void

emit? cljs

(emit? fs-watcher event-name & args)

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

Parameters:

• event-name: string | symbol
• args: AnyRest

Returns: boolean

event-names cljs

(event-names fs-watcher)

Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or Symbols.

import { EventEmitter } from 'node:events';

const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});

const sym = Symbol('symbol');
myEE.on(sym, () => {});

console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]

Returns: (string | symbol)[]

listener-count cljs

(listener-count fs-watcher event-name)

(listener-count fs-watcher event-name listener)

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.

Parameters:

• event-name: string | symbol - The name of the event being listened for
• listener: Function | undefined - The event handler function

Returns: number

listeners cljs

(listeners fs-watcher event-name)

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] ]

Parameters:

• event-name: string | symbol

Returns: Function[]

max-listeners cljs

(max-listeners fs-watcher)

Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to {@link defaultMaxListeners }.

Returns: number

off cljs

(off fs-watcher event-name listener)

Alias for emitter.removeListener().

Parameters:

• event-name: string | symbol
• listener: (...args: any[]) => void

Returns: FSWatcher

on cljs

(on fs-watcher event listener)

Parameters:

• event: "error"
• listener: (error: Error) => void

Returns: FSWatcher

once cljs

(once fs-watcher event listener)

Parameters:

• event: "error"
• listener: (error: Error) => void

Returns: FSWatcher

prepend-listener cljs

(prepend-listener fs-watcher event listener)

Parameters:

• event: "error"
• listener: (error: Error) => void

Returns: FSWatcher

prepend-once-listener cljs

(prepend-once-listener fs-watcher event listener)

Parameters:

• event: "error"
• listener: (error: Error) => void

Returns: FSWatcher

raw-listeners cljs

(raw-listeners fs-watcher event-name)

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');

Parameters:

• event-name: string | symbol

Returns: Function[]

ref cljs

(ref fs-watcher)

When called, requests that the Node.js event loop not exit so long as the fs.FSWatcher is active. Calling watcher.ref() multiple times will have no effect.

By default, all fs.FSWatcher objects are "ref'ed", making it normally unnecessary to call watcher.ref() unless watcher.unref() had been called previously.

Returns: FSWatcher

remove-all-listeners cljs

(remove-all-listeners fs-watcher)

(remove-all-listeners fs-watcher event-name)

Removes all listeners, or those of the specified eventName.

It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters:

• event-name: string | symbol | undefined

Returns: FSWatcher

remove-listener cljs

(remove-listener fs-watcher event-name listener)

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.

Parameters:

• event-name: string | symbol
• listener: (...args: any[]) => void

Returns: FSWatcher

set-max-listeners cljs

(set-max-listeners fs-watcher n)

By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) to indicate an unlimited number of listeners.

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters:

• n: number

Returns: FSWatcher

unref cljs

(unref fs-watcher)

When called, the active fs.FSWatcher 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 the fs.FSWatcher object's callback is invoked. Calling watcher.unref() multiple times will have no effect.

Returns: FSWatcher