events: add off alias to removeListener

Add `off` as an alias for `removeListener`

PR-URL: https://github.com/nodejs/node/pull/17156
Refs: https://github.com/nodejs/node/issues/17102
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jan Krems <jan.krems@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Benedikt Meurer <benedikt.meurer@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Khaidi Chu <i@2333.moe>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

lib/events.js

@@ -307,6 +307,8 @@ EventEmitter.prototype.removeListener =
       return this;
     };
 
+EventEmitter.prototype.off = EventEmitter.prototype.removeListener;
+
 EventEmitter.prototype.removeAllListeners =
     function removeAllListeners(type) {
       var listeners, events, i;

test/parallel/test-event-emitter-method-names.js

@@ -27,8 +27,9 @@ const events = require('events');
 const E = events.EventEmitter.prototype;
 assert.strictEqual(E.constructor.name, 'EventEmitter');
 assert.strictEqual(E.on, E.addListener);  // Same method.
+assert.strictEqual(E.off, E.removeListener);  // Same method.
 Object.getOwnPropertyNames(E).forEach(function(name) {
-  if (name === 'constructor' || name === 'on') return;
+  if (name === 'constructor' || name === 'on' || name === 'off') return;
   if (typeof E[name] !== 'function') return;
   assert.strictEqual(E[name].name, name);
 });