simplify get language code

Author: fadi-george

package.json

@@ -84,7 +84,7 @@
     },
     {
       "path": "./build/releases/OneSignalSDK.page.es6.js",
-      "limit": "45.364 kB",
+      "limit": "45.322 kB",
       "gzip": true
     },
     {

src/core/executors/LoginUserOperationExecutor.ts

@@ -335,34 +335,16 @@ export class LoginUserOperationExecutor implements IOperationExecutor {
   }
 }
 
-const TRADITIONAL_CHINESE_LANGUAGE_TAG = ['tw', 'hant'];
 const SIMPLIFIED_CHINESE_LANGUAGE_TAG = ['cn', 'hans'];
 
 const getLanguage = () => {
-  let languageTag = navigator.language;
-  if (languageTag) {
-    languageTag = languageTag.toLowerCase();
-    const languageSubtags = languageTag.split('-');
-    if (languageSubtags[0] == 'zh') {
-      // The language is zh-?
-      // We must categorize the language as either zh-Hans (simplified) or zh-Hant (traditional);
-      // OneSignal only supports these two Chinese variants
-      for (const traditionalSubtag of TRADITIONAL_CHINESE_LANGUAGE_TAG) {
-        if (languageSubtags.indexOf(traditionalSubtag) !== -1) {
-          return 'zh-Hant';
-        }
-      }
-      for (const simpleSubtag of SIMPLIFIED_CHINESE_LANGUAGE_TAG) {
-        if (languageSubtags.indexOf(simpleSubtag) !== -1) {
-          return 'zh-Hans';
-        }
-      }
-      return 'zh-Hant'; // Return Chinese traditional by default
-    } else {
-      // Return the language subtag (it can be three characters, so truncate it down to 2 just to be sure)
-      return languageSubtags[0].substring(0, 2);
-    }
-  } else {
-    return 'en';
-  }
+  const languageTag = navigator.language?.toLowerCase();
+  if (!languageTag) return 'en';
+
+  const [primary, ...subtags] = languageTag.split('-');
+  if (primary !== 'zh') return primary.substring(0, 2);
+
+  if (SIMPLIFIED_CHINESE_LANGUAGE_TAG.some((tag) => subtags.includes(tag)))
+    return 'zh-Hans';
+  return 'zh-Hant';
 };