chore(language): make normalize function more readable through destru…

…cturing (#6094)

lib/util/language_utils.js

@@ -192,25 +192,24 @@ shaka.util.LanguageUtils = class {
     const LanguageUtils = shaka.util.LanguageUtils;
 
     const privateusePrefix = 'x-';
-    const components = locale.split(`-${privateusePrefix}`);
-    const languageAndRegion = components[0].split('-');
+    const [languageRegion = '', privateuseSuffix = ''] =
+     locale.split(`-${privateusePrefix}`);
+    const [languageCode = '', regionCode = ''] = languageRegion.split('-');
 
     // We are only going to use the language, the region and the "privateuse" part (as per https://datatracker.ietf.org/doc/html/rfc5646).
     // Anything else is thrown away.
-    let language = languageAndRegion[0] || '';
-    let region = languageAndRegion[1] || '';
-    const privateuse = components[1] ?
-        `${privateusePrefix}${components[1]}` : '';
+    const privateuse = privateuseSuffix ?
+        `${privateusePrefix}${privateuseSuffix}` : '';
 
     // Convert the language to lower case. It is standard for the language code
     // to be in lower case, but it will also make the map look-up easier.
-    language = language.toLowerCase();
+    let language = languageCode.toLowerCase();
     language = LanguageUtils.isoMap_.get(language) || language;
 
     // Convert the region to upper case. It is standard for the region to be in
     // upper case. If there is no upper code, then it will be an empty string
     // and this will be a no-op.
-    region = region.toUpperCase();
+    const region = regionCode.toUpperCase();
 
     return `${region ? `${language}-${region}` : language}${
         privateuse ? `-${privateuse}` : ''}`;