events: optimize condition for optimal scenario

Instead of always checking whether we've already warned about a
possible EventEmitter memory leak, first run the rest of the
code as accessing random properties on an Array is expensive.
In addition, remove an unnecessary truthy check.
PR-URL: #20452
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

Author: apapirovski

benchmark/events/ee-add-remove.js

@@ -2,7 +2,7 @@
 constcommon=require('../common.js');
 constevents=require('events');
 
-constbench=common.createBenchmark(main,{n: [25e4]});
+constbench=common.createBenchmark(main,{n: [1e6]});
 
 functionmain({ n }){
 constee=newevents.EventEmitter();

lib/events.js

@@ -235,22 +235,20 @@ function _addListener(target, type, listener, prepend) {
 }
 
 // Check for listener leak
-if(!existing.warned){
-m=$getMaxListeners(target);
-if(m&&m>0&&existing.length>m){
-existing.warned=true;
-// No error code for this since it is a Warning
-// eslint-disable-next-line no-restricted-syntax
-constw=newError('Possible EventEmitter memory leak detected. '+
-`${existing.length}${String(type)} listeners `+
-'added. Use emitter.setMaxListeners() to '+
-'increase limit');
-w.name='MaxListenersExceededWarning';
-w.emitter=target;
-w.type=type;
-w.count=existing.length;
-process.emitWarning(w);
-}
+m=$getMaxListeners(target);
+if(m>0&&existing.length>m&&!existing.warned){
+existing.warned=true;
+// No error code for this since it is a Warning
+// eslint-disable-next-line no-restricted-syntax
+constw=newError('Possible EventEmitter memory leak detected. '+
+`${existing.length}${String(type)} listeners `+
+'added. Use emitter.setMaxListeners() to '+
+'increase limit');
+w.name='MaxListenersExceededWarning';
+w.emitter=target;
+w.type=type;
+w.count=existing.length;
+process.emitWarning(w);
 }
 }