performance patch for @formatjs/intl-datetimeformat@4.1.5

dtf-perf.diff

diff --git a/src/abstract/FormatDateTimePattern.js b/src/abstract/FormatDateTimePattern.js
index 47fd27397f6fff014af1c4b8862e26fea11e7aab..8d0d1234d9a5dcbd6131bbe206d4655a6c153726 100755
--- a/src/abstract/FormatDateTimePattern.js
+++ b/src/abstract/FormatDateTimePattern.js
@@ -32,6 +32,28 @@ function offsetToGmtString(gmtFormat, hourFormat, offsetInMs, style) {
     }
     return gmtFormat.replace('{0}', offsetStr);
 }
+var numberFormatsCache = new Map();
+function getNumberFormatsForLocale(locale, fractionalSecondDigits) {
+    var cache = numberFormatsCache.get(locale);
+    if (cache)
+        return cache;
+    var nfOptions = Object.create(null);
+    nfOptions.useGrouping = false;
+    var nf = new Intl.NumberFormat(locale, nfOptions);
+    var nf2Options = Object.create(null);
+    nf2Options.minimumIntegerDigits = 2;
+    nf2Options.useGrouping = false;
+    var nf2 = new Intl.NumberFormat(locale, nf2Options);
+    var nf3 = undefined;
+    if (fractionalSecondDigits !== undefined) {
+        var nf3Options = Object.create(null);
+        nf3Options.minimumIntegerDigits = fractionalSecondDigits;
+        nf3Options.useGrouping = false;
+        nf3 = new Intl.NumberFormat(locale, nf3Options);
+    }
+    numberFormatsCache.set(locale, [nf, nf2, nf3]);
+    return [nf, nf2, nf3];
+}
 /**
  * https://tc39.es/ecma402/#sec-partitiondatetimepattern
  * @param dtf
@@ -45,22 +67,8 @@ function FormatDateTimePattern(dtf, patternParts, x, _a) {
     var dataLocale = internalSlots.dataLocale;
     var dataLocaleData = localeData[dataLocale];
     /** IMPL END */
-    var locale = internalSlots.locale;
-    var nfOptions = Object.create(null);
-    nfOptions.useGrouping = false;
-    var nf = new Intl.NumberFormat(locale, nfOptions);
-    var nf2Options = Object.create(null);
-    nf2Options.minimumIntegerDigits = 2;
-    nf2Options.useGrouping = false;
-    var nf2 = new Intl.NumberFormat(locale, nf2Options);
     var fractionalSecondDigits = internalSlots.fractionalSecondDigits;
-    var nf3;
-    if (fractionalSecondDigits !== undefined) {
-        var nf3Options = Object.create(null);
-        nf3Options.minimumIntegerDigits = fractionalSecondDigits;
-        nf3Options.useGrouping = false;
-        nf3 = new Intl.NumberFormat(locale, nf3Options);
-    }
+    var _b = getNumberFormatsForLocale(internalSlots.locale, fractionalSecondDigits), nf = _b[0], nf2 = _b[1], nf3 = _b[2];
     var tm = ToLocalTime_1.ToLocalTime(x, 
     // @ts-ignore
     internalSlots.calendar, internalSlots.timeZone, { tzData: tzData });

There's a gap in the specification that results in some polyfills (formatjs in particular) being incredibly slow: tc39/ecma402#563 This has a PR at: tc39/ecma402#569

This results in this issue with the Hermes JS engine on React Native, especially on Android. facebook/hermes#23 (comment)

Here's one way to fix it: formatjs/formatjs#2827