Finalize fallback option

Author: yauhenipakala

README.md

@@ -77,6 +77,7 @@ After version 1.1.0 plugin has optional parameter `options` - for custom setup:
 version | name          | type    | default value | description
 --------|---------------|---------|---------------|-----------------------
 v1.1.0  | overrideNames | object  | {}            | [Override the default language names](#overrideNames)
+v1.1.1  | fallback    | func(str): str | (lang) => lang | [Fallback to convert unknown names](#fallback)
 
 ### Examples of using
 
@@ -118,6 +119,26 @@ In both cases language name will be `C#`.
 
 > [List of default language names](https://github.com/wcoder/highlightjs-lang.js/blob/master/src/highlightjs-lang.js#L4-L10)
 
+### fallback
+
+Specifying the desired format for undeclared language names:
+
+```js
+var myOptions = {
+  // ...
+  fallback: function (lang) {
+    return '~~' + lang;
+  },
+  // ...
+};
+```
+
+Convert all undeclared language names to names with `~~` prefix:
+
+```
+xyz -> ~~xyz
+```
+
 ## Skipping some blocks
 
 (Applies to `hljs.initLangOnLoad()` initialization only.)

dist/highlightjs-lang.min.js

@@ -17,11 +17,19 @@
   <script src="dist/highlightjs-lang.min.js"></script>
   <script>
     hljs.highlightAll();
+
+    // init plugin:
     hljs.initLangOnLoad(
     {
       overrideNames: {
-        cpp: 'C++',
-      }
+        dart: 'Dart',
+      },
+      fallback: function (lang) {
+        if (lang === 'php') {
+          return '$ PHP $';
+        }
+        return lang;
+      },
     }
     );
   </script>

index.html

@@ -98,15 +98,8 @@
       : defaultFallbackOption;
   }
 
-  function defaultFallbackOption (codeLang) {
-    if (!!codeLang) {
-      var lang = codeLang.trim();
-      if (lang.length > 0) {
-        lang[0] = lang[0].toUpperCase();
-        return lang;
-      }
-    }
-    return codeLang;
+  function defaultFallbackOption (langKey) {
+    return langKey;
   }
 
   function getLangNameFromElement (element) {