From 959f0a2204822a5eac8d8186e585ae196c820495 Mon Sep 17 00:00:00 2001
From: shirakaba <14055146+shirakaba@users.noreply.github.com>
Date: Wed, 21 Dec 2022 21:42:31 +0900
Subject: [PATCH] fix: swap spread for slice

---
 packages/core/data/dom-events/dom-event.ts | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/packages/core/data/dom-events/dom-event.ts b/packages/core/data/dom-events/dom-event.ts
index 6cd8f09da..3c49d499a 100644
--- a/packages/core/data/dom-events/dom-event.ts
+++ b/packages/core/data/dom-events/dom-event.ts
@@ -365,8 +365,14 @@ export class DOMEvent implements Event {
 	// Taking multiple params instead of a single property bag saves 250
 	// nanoseconds per dispatchTo() call.
 	private handleEvent(data: EventData, isGlobal: boolean, phase: 0 | 1 | 2 | 3, removeEventListener: (eventName: string, callback?: any, thisArg?: any, capture?: boolean) => void, removeEventListenerContext: unknown) {
-		// Clone the array just before any mutations.
-		const listeners = [...this.listeners];
+		// Clone the array just before any mutations. I tried swapping this out
+		// for a copy-on-write array, but as it had to maintain its own array of
+		// listeners for any write actions, it actually ran significantly
+		// slower.
+		//
+		// There's no clear observable difference between array spread and slice
+		// here, but I think slice has reason to run faster.
+		const listeners = this.listeners.slice();
 
 		for (let i = listeners.length - 1; i >= 0; i--) {
 			const listener = listeners[i];