events: speed up emit by faster null prototype object

nodejs · Aug 30, 2021 · 66fcbef · 66fcbef
1 parent 449147e
commit 66fcbef
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Showing 2 changed files with 16 additions and 8 deletions.
diff --git a/benchmark/events/ee-emit.js b/benchmark/events/ee-emit.js
@@ -5,7 +5,7 @@ const EventEmitter = require('events').EventEmitter;
 const bench = common.createBenchmark(main, {
   n: [2e6],
   argc: [0, 2, 4, 10],
-  listeners: [1, 5, 10],
+  listeners: [0, 1, 5, 10],
 });
 
 function main({ n, argc, listeners }) {

diff --git a/lib/events.js b/lib/events.js
@@ -34,7 +34,6 @@ const {
   FunctionPrototypeCall,
   MathMin,
   NumberIsNaN,
-  ObjectCreate,
   ObjectDefineProperty,
   ObjectDefineProperties,
   ObjectGetPrototypeOf,
@@ -127,6 +126,15 @@ EventEmitter.prototype._maxListeners = undefined;
 let defaultMaxListeners = 10;
 let isEventTarget;
 
+// We need to create null prototype to prevent internal method like `toString`
+// mess with event handling. In current version v8, Object create by
+// `ObjectSetPrototypeOf` is much more efficient than `ObjectCreate(null)`
+function objectCreateNull() {
+  const events = {};
+  ObjectSetPrototypeOf(events, null);
+  return events;
+}
+
 function checkListener(listener) {
   validateFunction(listener, 'listener');
 }
@@ -198,7 +206,7 @@ EventEmitter.init = function(opts) {
 
   if (this._events === undefined ||
       this._events === ObjectGetPrototypeOf(this)._events) {
-    this._events = ObjectCreate(null);
+    this._events = objectCreateNull();
     this._eventsCount = 0;
   }
 
@@ -428,7 +436,7 @@ function _addListener(target, type, listener, prepend) {
 
   events = target._events;
   if (events === undefined) {
-    events = target._events = ObjectCreate(null);
+    events = target._events = objectCreateNull();
     target._eventsCount = 0;
   } else {
     // To avoid recursion in the case that type === "newListener"! Before
@@ -571,7 +579,7 @@ EventEmitter.prototype.removeListener =
 
       if (list === listener || list.listener === listener) {
         if (--this._eventsCount === 0)
-          this._events = ObjectCreate(null);
+          this._events = objectCreateNull();
         else {
           delete events[type];
           if (events.removeListener)
@@ -626,11 +634,11 @@ EventEmitter.prototype.removeAllListeners =
       // Not listening for removeListener, no need to emit
       if (events.removeListener === undefined) {
         if (arguments.length === 0) {
-          this._events = ObjectCreate(null);
+          this._events = objectCreateNull();
           this._eventsCount = 0;
         } else if (events[type] !== undefined) {
           if (--this._eventsCount === 0)
-            this._events = ObjectCreate(null);
+            this._events = objectCreateNull();
           else
             delete events[type];
         }
@@ -644,7 +652,7 @@ EventEmitter.prototype.removeAllListeners =
           this.removeAllListeners(key);
         }
         this.removeAllListeners('removeListener');
-        this._events = ObjectCreate(null);
+        this._events = objectCreateNull();
         this._eventsCount = 0;
         return this;
       }