From 601ee1fd7d313c4acfd1f1d369c15376fcc51707 Mon Sep 17 00:00:00 2001
From: himself65 <himself6565@gmail.com>
Date: Fri, 26 Apr 2019 13:10:24 +0800
Subject: [PATCH] lib: bind functions on EventEmitter

---
 lib/events.js                                 | 19 ++++++++
 ...test-event-emitter-check-bind-functions.js | 43 +++++++++++++++++++
 .../test-event-emitter-method-names.js        |  4 +-
 3 files changed, 65 insertions(+), 1 deletion(-)
 create mode 100644 test/parallel/test-event-emitter-check-bind-functions.js

diff --git a/lib/events.js b/lib/events.js
index 3deb155479187f..346ff7cda5bfba 100644
--- a/lib/events.js
+++ b/lib/events.js
@@ -266,6 +266,9 @@ function _addListener(target, type, listener, prepend) {
   return target;
 }
 
+bindEventEmitterFunction('addListener', '_addListener');
+bindEventEmitterFunction('on', '_addListener');
+
 EventEmitter.prototype.addListener = function addListener(type, listener) {
   return _addListener(this, type, listener, false);
 };
@@ -308,6 +311,9 @@ EventEmitter.prototype.prependOnceListener =
       return this;
     };
 
+bindEventEmitterFunction('removeListener', '_removeListener');
+bindEventEmitterFunction('off', '_removeListener');
+
 // Emits a 'removeListener' event if and only if the listener was removed.
 EventEmitter.prototype.removeListener =
     function removeListener(type, listener) {
@@ -508,3 +514,16 @@ function once(emitter, name) {
     emitter.once(name, eventListener);
   });
 }
+
+function bindEventEmitterFunction(name, target) {
+  Object.defineProperty(EventEmitter.prototype, name, {
+    configurable: true,
+    enumerable: true,
+    set: function(newVal) {
+      this[target] = newVal;
+    },
+    get: function() {
+      return this[target];
+    }
+  });
+}
diff --git a/test/parallel/test-event-emitter-check-bind-functions.js b/test/parallel/test-event-emitter-check-bind-functions.js
new file mode 100644
index 00000000000000..ee4a40d7ae8d49
--- /dev/null
+++ b/test/parallel/test-event-emitter-check-bind-functions.js
@@ -0,0 +1,43 @@
+'use strict';
+require('../common');
+const assert = require('assert');
+const events = require('events');
+
+{
+  const E = events.EventEmitter.prototype;
+
+  assert.strictEqual(E.on, E.addListener);
+  assert.strictEqual(E.off, E.removeListener);
+
+  E.on = function() {};
+  assert.strictEqual(E.on, E.addListener);
+
+  E.addListener = function() {};
+  assert.strictEqual(E.on, E.addListener);
+
+  E.off = function() {};
+  assert.strictEqual(E.off, E.removeListener);
+
+  E.removeListener = function() {};
+  assert.strictEqual(E.off, E.removeListener);
+}
+
+{
+  const EventEmitter = events.EventEmitter;
+
+  const ee = new EventEmitter();
+
+  assert.strictEqual(ee.on, ee.addListener);
+
+  ee.on = function() {};
+  assert.strictEqual(ee.on, ee.addListener);
+
+  ee.addListener = function() {};
+  assert.strictEqual(ee.on, ee.addListener);
+
+  ee.off = function() {};
+  assert.strictEqual(ee.off, ee.removeListener);
+
+  ee.removeListener = function() {};
+  assert.strictEqual(ee.off, ee.removeListener);
+}
diff --git a/test/parallel/test-event-emitter-method-names.js b/test/parallel/test-event-emitter-method-names.js
index 684024d0276261..eff4e68c1d48a4 100644
--- a/test/parallel/test-event-emitter-method-names.js
+++ b/test/parallel/test-event-emitter-method-names.js
@@ -29,7 +29,9 @@ 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' || name === 'off') return;
+  if (name === 'constructor' || name === 'on' || name === 'off' ||
+      name === '_addListener' || name === '_removeListener')
+    return;
   if (typeof E[name] !== 'function') return;
   assert.strictEqual(E[name].name, name);
 });