From 842e86cd4c513c6fb15b81604662b7aa5693c0fe Mon Sep 17 00:00:00 2001
From: Alexander Zinchuk <alx.zinchuk@gmail.com>
Date: Tue, 9 Nov 2021 21:21:33 +0300
Subject: [PATCH] [Perf] Message List: Avoid `toLocaleTimeString` because of
 bad performance

---
 src/components/middle/composer/Composer.tsx |  2 +-
 src/util/dateFormat.ts                      | 14 ++++++++------
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/components/middle/composer/Composer.tsx b/src/components/middle/composer/Composer.tsx
index 410083a54..7b137e631 100644
--- a/src/components/middle/composer/Composer.tsx
+++ b/src/components/middle/composer/Composer.tsx
@@ -409,7 +409,7 @@ const Composer: FC<OwnProps & StateProps & DispatchProps> = ({
     closeEmojiTooltip();
 
     if (IS_SINGLE_COLUMN_LAYOUT) {
-      // @perf
+      // @optimization
       setTimeout(() => closeSymbolMenu(), SENDING_ANIMATION_DURATION);
     } else {
       closeSymbolMenu();
diff --git a/src/util/dateFormat.ts b/src/util/dateFormat.ts
index ad7af402b..47e37437c 100644
--- a/src/util/dateFormat.ts
+++ b/src/util/dateFormat.ts
@@ -31,17 +31,19 @@ function toIsoString(date: Date) {
   return `${date.getFullYear()}-${date.getMonth() + 1}-${date.getDate()}`;
 }
 
+// @optimization `toLocaleTimeString` is avoided because of bad performance
 export function formatTime(datetime: number | Date, lang: LangFn) {
   const date = typeof datetime === 'number' ? new Date(datetime) : datetime;
   const timeFormat = lang.timeFormat || '24h';
 
-  const time = date.toLocaleTimeString(lang.code, {
-    hour12: timeFormat === '12h',
-    hour: timeFormat === '12h' ? 'numeric' : '2-digit',
-    minute: '2-digit',
-  });
+  let hours = date.getHours();
+  let marker = '';
+  if (timeFormat === '12h') {
+    marker = hours >= 12 ? ' PM' : ' AM';
+    hours %= 12;
+  }
 
-  return timeFormat === '12h' ? time.replace(/^0:/, '12:') : time.replace('24:', '00:');
+  return `${String(hours).padStart(2, '0')}:${String(date.getMinutes()).padStart(2, '0')}${marker}`;
 }
 
 export function formatPastTimeShort(lang: LangFn, datetime: number | Date) {