html10n: fix variant only langs (e.g zh-*); add comments

src/static/js/html10n.js

@@ -179,21 +179,33 @@ window.html10n = (function(window, document, undefined) {
       return
     }
 
-    // dat alng ain't here, man!
+    // Check if lang exists
     if (!data[lang]) {
+      // lang not found
+      // This may be due to formatting (expected 'ru' but browser sent 'ru-RU')
+      // Set err msg before mutating lang (we may need this later)
+      var msg = 'Couldn\'t find translations for '+lang
+      // Check for '-' ('ROOT-VARIANT')
       if (lang.indexOf('-') > -1) {
-        var msg = 'Couldn\'t find translations for '+lang
-        lang = lang.split('-')[0] // get root locale incase variant (e.g ru-RU)
-        if (!data[lang]) { // check root locale (e.g ru)
-          var l
-          for(l in data) { // try similar (e.g zh-hans)
-            if(lang != l && l.indexOf(lang) === 0 && data[l]) {
-              lang = l
-              break;
-            }
+        // ROOT-VARIANT formatting detected
+        lang = lang.split('-')[0] // set lang to ROOT lang
+      }
+      // Check if ROOT lang exists (e.g 'ru')
+      if (!data[lang]) {
+        // ROOT lang not found. (e.g 'zh')
+        // Loop through langs data. Maybe we have a variant? e.g (zh-hans)
+        var l // langs item. Declare outside of loop
+        for(l in data) {
+          // Is not ROOT?
+          // And index of ROOT equals 0?
+          // And is known lang?
+          if(lang != l && l.indexOf(lang) === 0 && data[l]) {
+            lang = l // set lang to ROOT-VARIANT (e.g 'zh-hans')
+            break;
           }
-          if(lang != l) return cb(new Error(msg))
         }
+        // Did we find a variant? If not, return err.
+        if(lang != l) return cb(new Error(msg))
       }
     }