events: add hasEventListener util for validate

There was some repetitive logics that validated the existence of eventlisteners. We now replace this with a single line of, `hasEventListener(self, type)`. `self` is the object(e.g. EventEmitter) to be checked whether eventlisteners exists or not. `type` is the type of eventlisteners, which can be `undefined` PR-URL: #55230 Reviewed-By: Jason Zhang <[email protected]>

Author: sungpaks

lib/events.js

@@ -287,6 +287,12 @@ ObjectDefineProperty(EventEmitter, 'defaultMaxListeners',{
 },
 });
 
+functionhasEventListener(self,type){
+if(type===undefined)
+returnself._events!==undefined;
+returnself._events!==undefined&&self._events[type]!==undefined;
+}
+
 ObjectDefineProperties(EventEmitter,{
 kMaxEventTargetListeners: {
 __proto__: null,
@@ -680,13 +686,11 @@ EventEmitter.prototype.removeListener =
 functionremoveListener(type,listener){
 checkListener(listener);
 
-constevents=this._events;
-if(events===undefined)
+if(!hasEventListener(this,type))
 returnthis;
 
+constevents=this._events;
 constlist=events[type];
-if(list===undefined)
-returnthis;
 
 if(list===listener||list.listener===listener){
 this._eventsCount-=1;
@@ -742,9 +746,9 @@ EventEmitter.prototype.off = EventEmitter.prototype.removeListener;
  */
 EventEmitter.prototype.removeAllListeners=
 functionremoveAllListeners(type){
-constevents=this._events;
-if(events===undefined)
+if(!hasEventListener(this))
 returnthis;
+constevents=this._events;
 
 // Not listening for removeListener, no need to emit
 if(events.removeListener===undefined){
@@ -789,14 +793,10 @@ EventEmitter.prototype.removeAllListeners =
 };
 
 function_listeners(target,type,unwrap){
-constevents=target._events;
-
-if(events===undefined)
+if(!hasEventListener(target,type))
 return[];
 
-constevlistener=events[type];
-if(evlistener===undefined)
-return[];
+constevlistener=target._events[type];
 
 if(typeofevlistener==='function')
 returnunwrap ? [evlistener.listener||evlistener] : [evlistener];