events: Make the EventEmitter class monomorphic

Always add domain, _events, and _maxListeners properties, set to the
default values at first.

Leads to a very very slight perf improvement when using setMaxListeners,
or dealing with a lot of EE objects that don't have any listeners.

1 files changed, 4 insertions, 5 deletions

diff --git a/lib/events.js b/lib/events.js
index e0af38066a..4ef2daed92 100644
--- a/lib/events.js
+++ b/lib/events.js
@@ -23,6 +23,7 @@ var isArray = Array.isArray;
 var domain;
 
 function EventEmitter() {
+  this.domain = null;
   if (exports.usingDomains) {
     // if there is an active domain, then attach to it.
     domain = domain || require('domain');
@@ -30,6 +31,8 @@ function EventEmitter() {
       this.domain = domain.active;
     }
   }
+  this._events = null;
+  this._maxListeners = defaultMaxListeners;
 }
 exports.EventEmitter = EventEmitter;
 
@@ -161,11 +164,7 @@ EventEmitter.prototype.addListener = function(type, listener) {
   // Check for listener leak
   if (isArray(this._events[type]) && !this._events[type].warned) {
     var m;
-    if (this._maxListeners !== undefined) {
-      m = this._maxListeners;
-    } else {
-      m = defaultMaxListeners;
-    }
+    m = this._maxListeners;
 
     if (m && m > 0 && this._events[type].length > m) {
       this._events[type].warned = true;