1 files changed, 18 insertions, 0 deletions
diff --git a/app/scripts/lib/get-first-preferred-lang-code.js b/app/scripts/lib/get-first-preferred-lang-code.js
new file mode 100644
index 000000000..e3635434e
--- /dev/null
+++ b/app/scripts/lib/get-first-preferred-lang-code.js
@@ -0,0 +1,18 @@
+const extension = require('extensionizer')
+const promisify = require('pify')
+const allLocales = require('../../_locales/index.json')
+
+const existingLocaleCodes = allLocales.map(locale => locale.code.toLowerCase().replace('_', '-'))
+
+async function getFirstPreferredLangCode () {
+  const userPreferredLocaleCodes = await promisify(
+    extension.i18n.getAcceptLanguages,
+    { errorFirst: false }
+  )()
+  const firstPreferredLangCode = userPreferredLocaleCodes
+    .map(code => code.toLowerCase())
+    .find(code => existingLocaleCodes.includes(code))
+  return firstPreferredLangCode || 'en'
+}
+
+module.exports = getFirstPreferredLangCode