Add Intl.NumberFormat cache.

ui/util/format-credits.js

@@ -1,3 +1,5 @@
+import { getFormatter } from './intlNumberFormat';
+
 export function formatCredits(amount, precision, shortFormat = false) {
   const language = localStorage.getItem('language') || undefined;
   const actualAmount = Number(amount);
@@ -6,7 +8,7 @@ export function formatCredits(amount, precision, shortFormat = false) {
   if (Number.isNaN(actualAmount) || actualAmount === 0) return '0';
 
   if (shortFormat) {
-    const formatter = new Intl.NumberFormat(language, {
+    const formatter = getFormatter(language, {
       minimumFractionDigits: safePrecision,
       maximumFractionDigits: safePrecision,
       roundingIncrement: 5,
@@ -17,7 +19,7 @@ export function formatCredits(amount, precision, shortFormat = false) {
     return formatter.format(actualAmount);
   }
 
-  const formatter = new Intl.NumberFormat(language, {
+  const formatter = getFormatter(language, {
     minimumFractionDigits: safePrecision,
     maximumFractionDigits: safePrecision,
     roundingIncrement: 5,

ui/util/intlNumberFormat.js

@@ -0,0 +1,14 @@
+// @flow
+const formatterCache = {};
+
+// Creating multiple Intl.NumberFormat instances can
+// be expensive, that's why we perform a very simple
+// cache.
+// See https://github.com/formatjs/formatjs/issues/27#issuecomment-61148808
+export function getFormatter(language?: string, options: any) {
+  const key = `${language || ''}:${JSON.stringify(options || {})}`;
+  if (!formatterCache[key]) {
+    formatterCache[key] = new Intl.NumberFormat(language, options);
+  }
+  return formatterCache[key];
+}

ui/util/number.js

@@ -1,9 +1,10 @@
 // @flow
+import { getFormatter } from './intlNumberFormat';
 
 export function formatNumber(num: number, numberOfDigits?: number, short: boolean = false): string {
   const language = localStorage.getItem('language') || undefined;
   const safePrecision = Math.min(20, numberOfDigits || 0);
-  const formatter = new Intl.NumberFormat(language, {
+  const formatter = getFormatter(language, {
     maximumFractionDigits: safePrecision,
     notation: short ? 'compact' : 'standard',
     compactDisplay: 'short',