From 3e9983cd0680fdf7836fcee638d34e3edc682380 Mon Sep 17 00:00:00 2001
From: Hasan Ozdemir <21654050+nodify-at@users.noreply.github.com>
Date: Wed, 4 Sep 2024 03:57:08 +0200
Subject: [PATCH] Optimize Performance with Caching for Resolved Options and
 Parsed Locale Strings (#1642)

* feat: optimize performance by adding caching for resolved options and parsed locale strings

- Implement caching to avoid redundant computations of resolved options and locale parsing.
- Introduce a final `isEnglish` variable to efficiently check if the locale supports English.

Signed-off-by: nodify-at <21654050+nodify-at@users.noreply.github.com>

* feat: simplify caching logic for resolved options in supportsFastNumbers and isEnglish calls to improve performance

Signed-off-by: nodify-at <21654050+nodify-at@users.noreply.github.com>

* feat: add new benchmark tests to compare performance with and without Intl.resolvedOptions cache

Signed-off-by: nodify-at <21654050+nodify-at@users.noreply.github.com>

---------

Signed-off-by: nodify-at <21654050+nodify-at@users.noreply.github.com>
---
 benchmarks/datetime.js |  7 +++++++
 src/impl/locale.js     | 14 +++++++++++---
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/benchmarks/datetime.js b/benchmarks/datetime.js
index f4dffda7b..aef549810 100644
--- a/benchmarks/datetime.js
+++ b/benchmarks/datetime.js
@@ -58,6 +58,13 @@ function runDateTimeSuite() {
         dt.toFormat("T");
         Settings.resetCaches();
       })
+      .add("DateTime#format in german", () => {
+        dt.setLocale("de-De").toFormat("d. LLL. HH:mm");
+      })
+      .add("DateTime#format in german and no-cache", () => {
+        dt.setLocale("de-De").toFormat("d. LLL. HH:mm");
+        Settings.resetCaches();
+      })
       .add("DateTime#add", () => {
         dt.plus({ milliseconds: 3434 });
       })
diff --git a/src/impl/locale.js b/src/impl/locale.js
index 93c489b07..b0ecc8c08 100644
--- a/src/impl/locale.js
+++ b/src/impl/locale.js
@@ -61,6 +61,14 @@ function systemLocale() {
   }
 }
 
+let intlResolvedOptionsCache = {};
+function getCachedIntResolvedOptions(locString) {
+  if (!intlResolvedOptionsCache[locString]) {
+    intlResolvedOptionsCache[locString] = new Intl.DateTimeFormat(locString).resolvedOptions();
+  }
+  return intlResolvedOptionsCache[locString];
+}
+
 let weekInfoCache = {};
 function getCachedWeekInfo(locString) {
   let data = weekInfoCache[locString];
@@ -167,7 +175,7 @@ function supportsFastNumbers(loc) {
       loc.numberingSystem === "latn" ||
       !loc.locale ||
       loc.locale.startsWith("en") ||
-      new Intl.DateTimeFormat(loc.intl).resolvedOptions().numberingSystem === "latn"
+      getCachedIntResolvedOptions(loc.locale).numberingSystem === "latn"
     );
   }
 }
@@ -326,7 +334,6 @@ const fallbackWeekSettings = {
 /**
  * @private
  */
-
 export default class Locale {
   static fromOpts(opts) {
     return Locale.create(
@@ -353,6 +360,7 @@ export default class Locale {
     intlDTCache = {};
     intlNumCache = {};
     intlRelCache = {};
+    intlResolvedOptionsCache = {};
   }
 
   static fromObject({ locale, numberingSystem, outputCalendar, weekSettings } = {}) {
@@ -506,7 +514,7 @@ export default class Locale {
     return (
       this.locale === "en" ||
       this.locale.toLowerCase() === "en-us" ||
-      new Intl.DateTimeFormat(this.intl).resolvedOptions().locale.startsWith("en-us")
+      getCachedIntResolvedOptions(this.intl).locale.startsWith("en-us")
     );
   }