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+# webpack
+
+## Removing unused languages from dynamic import
+
+If a locale is imported dynamically, then all locales from date-fns are loaded by webpack into a bundle (~160kb) or split across the chunks. This prolongs the build process and increases the amount of space taken. However, it is possible to use webpack to trim down languages using [ContextReplacementPlugin].
+
+Let's assume that we have a single point in which supported locales are present:
+
+`config.js`:
+
+```js
+// `see date-fns/src/locale` for available locales
+export const supportedLocales = ['en-US', 'de', 'pl', 'it']
+```
+
+We could also have a function that formats the date:
+
+```js
+const getLocale = (locale) => import(`date-fns/locale/${locale}/index.js`) // or require() if using CommonJS
+
+const formatDate = (date, formatStyle, locale) => {
+  return format(date, formatStyle, {
+    locale: getLocale(locale),
+  })
+}
+```
+
+In order to exclude unused languages we can use webpacks [ContextReplacementPlugin].
+
+`webpack.config.js`:
+
+```js
+import webpack from 'webpack'
+import { supportedLocales } from './config.js'
+
+export default const config = {
+  plugins: [
+    new webpack.ContextReplacementPlugin(
+      /date\-fns[\/\\]/,
+      new RegExp(`[/\\\\\](${supportedLocales.join('|')})[/\\\\\]index\.js$`)
+    )
+  ]
+}
+```
+
+This results in a language bundle of ~23kb .
+
+[contextreplacementplugin]: https://webpack.js.org/plugins/context-replacement-plugin/