1 files changed, 55 insertions, 11 deletions

diff --git a/src/js/node/events.js b/src/js/node/events.js
index bd79dd3ae..0c7434518 100644
--- a/src/js/node/events.js
+++ b/src/js/node/events.js
@@ -14,7 +14,7 @@ const ArrayPrototypeSlice = Array.prototype.slice;
 
 var defaultMaxListeners = 10;
 
-// EventEmitter must be a standard function because some old code will do weird tricks like `EventEmitter.apply(this)`.
+// EventEmitter must be a standard function because some old code will do weird tricks like `EventEmitter.$apply(this)`.
 const EventEmitter = function EventEmitter(opts) {
   if (this._events === undefined || this._events === this.__proto__._events) {
     this._events = { __proto__: null };
@@ -49,14 +49,14 @@ function emitError(emitter, args) {
   if (!events) throw args[0];
   var errorMonitor = events[kErrorMonitor];
   if (errorMonitor) {
-    for (var handler of ArrayPrototypeSlice.call(errorMonitor)) {
-      handler.apply(emitter, args);
+    for (var handler of ArrayPrototypeSlice.$call(errorMonitor)) {
+      handler.$apply(emitter, args);
     }
   }
   var handlers = events.error;
   if (!handlers) throw args[0];
-  for (var handler of ArrayPrototypeSlice.call(handlers)) {
-    handler.apply(emitter, args);
+  for (var handler of ArrayPrototypeSlice.$call(handlers)) {
+    handler.$apply(emitter, args);
   }
   return true;
 }
@@ -92,9 +92,30 @@ const emitWithoutRejectionCapture = function emit(type, ...args) {
   if (events === undefined) return false;
   var handlers = events[type];
   if (handlers === undefined) return false;
-
-  for (var handler of [...handlers]) {
-    handler.apply(this, args);
+  // Clone handlers array if necessary since handlers can be added/removed during the loop.
+  // Cloning is skipped for performance reasons in the case of exactly one attached handler
+  // since array length changes have no side-effects in a for-loop of length 1.
+  const maybeClonedHandlers = handlers.length > 1 ? handlers.slice() : handlers;
+  for (let i = 0, { length } = maybeClonedHandlers; i < length; i++) {
+    const handler = maybeClonedHandlers[i];
+    // For performance reasons Function.call(...) is used whenever possible.
+    switch (args.length) {
+      case 0:
+        handler.$call(this);
+        break;
+      case 1:
+        handler.$call(this, args[0]);
+        break;
+      case 2:
+        handler.$call(this, args[0], args[1]);
+        break;
+      case 3:
+        handler.$call(this, args[0], args[1], args[2]);
+        break;
+      default:
+        handler.$apply(this, args);
+        break;
+    }
   }
   return true;
 };
@@ -107,8 +128,31 @@ const emitWithRejectionCapture = function emit(type, ...args) {
   if (events === undefined) return false;
   var handlers = events[type];
   if (handlers === undefined) return false;
-  for (var handler of [...handlers]) {
-    var result = handler.apply(this, args);
+  // Clone handlers array if necessary since handlers can be added/removed during the loop.
+  // Cloning is skipped for performance reasons in the case of exactly one attached handler
+  // since array length changes have no side-effects in a for-loop of length 1.
+  const maybeClonedHandlers = handlers.length > 1 ? handlers.slice() : handlers;
+  for (let i = 0, { length } = maybeClonedHandlers; i < length; i++) {
+    const handler = maybeClonedHandlers[i];
+    let result;
+    // For performance reasons Function.call(...) is used whenever possible.
+    switch (args.length) {
+      case 0:
+        result = handler.$call(this);
+        break;
+      case 1:
+        result = handler.$call(this, args[0]);
+        break;
+      case 2:
+        result = handler.$call(this, args[0], args[1]);
+        break;
+      case 3:
+        result = handler.$call(this, args[0], args[1], args[2]);
+        break;
+      default:
+        result = handler.$apply(this, args);
+        break;
+    }
     if (result !== undefined && $isPromise(result)) {
       addCatch(this, result, type, args);
     }
@@ -181,7 +225,7 @@ function overflowWarning(emitter, type, handlers) {
 
 function onceWrapper(type, listener, ...args) {
   this.removeListener(type, listener);
-  listener.apply(this, args);
+  listener.$apply(this, args);
 }
 
 EventEmitterPrototype.once = function once(type, fn) {