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events: add listener argument to listenerCount · nodejs/node@2eb8875 · GitHub

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ShogunPanda
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events: add listener argument to listenerCount
PR-URL: #46523 Reviewed-By: Robert Nagy <ronagy@icloud.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
1 parent 19b5d07 commit 2eb8875

4 files changed

Lines changed: 82 additions & 5 deletions

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‎doc/api/deprecations.md‎

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@@ -3373,7 +3373,7 @@ In a future version of Node.js, [`message.headers`][],
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[`dnsPromises.lookup()`]: dns.md#dnspromiseslookuphostname-options
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[`domain`]: domain.md
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[`ecdh.setPublicKey()`]: crypto.md#ecdhsetpublickeypublickey-encoding
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[`emitter.listenerCount(eventName)`]: events.md#emitterlistenercounteventname
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[`emitter.listenerCount(eventName)`]: events.md#emitterlistenercounteventname-listener
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[`events.listenerCount(emitter, eventName)`]: events.md#eventslistenercountemitter-eventname
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[`fs.FileHandle`]: fs.md#class-filehandle
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[`fs.access()`]: fs.md#fsaccesspath-mode-callback

‎doc/api/events.md‎

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@@ -646,16 +646,23 @@ Returns the current max listener value for the `EventEmitter` which is either
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set by [`emitter.setMaxListeners(n)`][] or defaults to
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[`events.defaultMaxListeners`][].
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### `emitter.listenerCount(eventName)`
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### `emitter.listenerCount(eventName[, listener])`
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<!-- YAML
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added: v3.2.0
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changes:
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- version: REPLACEME
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pr-url: https://github.com/nodejs/node/pull/46523
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description: Added the `listener` argument.
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-->
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* `eventName` {string|symbol} The name of the event being listened for
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* `listener` {Function} The event handler function
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* Returns: {integer}
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Returns the number of listeners listening to the event named `eventName`.
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Returns the number of listeners listening for the event named `eventName`.
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If `listener` is provided, it will return how many times the listener is found
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in the list of the listeners of the event.
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### `emitter.listeners(eventName)`
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@@ -2482,7 +2489,7 @@ to the `EventTarget`.
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[`EventTarget` error handling]: #eventtarget-error-handling
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[`Event` Web API]: https://dom.spec.whatwg.org/#event
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[`domain`]: domain.md
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[`emitter.listenerCount()`]: #emitterlistenercounteventname
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[`emitter.listenerCount()`]: #emitterlistenercounteventname-listener
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[`emitter.removeListener()`]: #emitterremovelistenereventname-listener
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[`emitter.setMaxListeners(n)`]: #emittersetmaxlistenersn
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[`event.defaultPrevented`]: #eventdefaultprevented

‎lib/events.js‎

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@@ -834,17 +834,34 @@ EventEmitter.prototype.listenerCount = listenerCount;
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* Returns the number of listeners listening to event name
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* specified as `type`.
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* @param {string | symbol} type
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* @param {Function} listener
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* @returns {number}
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*/
839-
function listenerCount(type) {
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function listenerCount(type, listener) {
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const events = this._events;
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if (events !== undefined) {
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const evlistener = events[type];
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if (typeof evlistener === 'function') {
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if (listener != null) {
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return listener === evlistener ? 1 : 0;
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}
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return 1;
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} else if (evlistener !== undefined) {
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if (listener != null) {
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let matching = 0;
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for (let i = 0, l = evlistener.length; i < l; i++) {
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if (evlistener[i] === listener || evlistener[i].listener === listener) {
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matching++;
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}
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}
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return matching;
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}
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return evlistener.length;
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}
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}

‎test/parallel/test-events-listener-count-with-listener.js‎

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@@ -0,0 +1,53 @@
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'use strict';
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const common = require('../common');
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const EventEmitter = require('events');
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const assert = require('assert');
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const EE = new EventEmitter();
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const handler = common.mustCall(undefined, 3);
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const anotherHandler = common.mustCall();
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assert.strictEqual(EE.listenerCount('event'), 0);
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assert.strictEqual(EE.listenerCount('event', handler), 0);
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assert.strictEqual(EE.listenerCount('event', anotherHandler), 0);
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EE.on('event', handler);
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assert.strictEqual(EE.listenerCount('event'), 1);
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assert.strictEqual(EE.listenerCount('event', handler), 1);
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assert.strictEqual(EE.listenerCount('event', anotherHandler), 0);
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EE.once('event', anotherHandler);
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assert.strictEqual(EE.listenerCount('event'), 2);
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assert.strictEqual(EE.listenerCount('event', handler), 1);
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assert.strictEqual(EE.listenerCount('event', anotherHandler), 1);
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assert.strictEqual(EE.listenerCount('another-event'), 0);
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assert.strictEqual(EE.listenerCount('another-event', handler), 0);
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assert.strictEqual(EE.listenerCount('another-event', anotherHandler), 0);
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EE.once('event', handler);
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assert.strictEqual(EE.listenerCount('event'), 3);
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assert.strictEqual(EE.listenerCount('event', handler), 2);
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assert.strictEqual(EE.listenerCount('event', anotherHandler), 1);
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EE.emit('event');
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assert.strictEqual(EE.listenerCount('event'), 1);
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assert.strictEqual(EE.listenerCount('event', handler), 1);
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assert.strictEqual(EE.listenerCount('event', anotherHandler), 0);
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EE.emit('event');
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assert.strictEqual(EE.listenerCount('event'), 1);
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assert.strictEqual(EE.listenerCount('event', handler), 1);
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assert.strictEqual(EE.listenerCount('event', anotherHandler), 0);
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EE.off('event', handler);
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assert.strictEqual(EE.listenerCount('event'), 0);
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assert.strictEqual(EE.listenerCount('event', handler), 0);
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assert.strictEqual(EE.listenerCount('event', anotherHandler), 0);

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