1 files changed, 30 insertions, 18 deletions
diff --git a/lib/output/modifiers/highlightCode.js b/lib/output/modifiers/highlightCode.js
index deabd68..dcd9d24 100644
--- a/lib/output/modifiers/highlightCode.js
+++ b/lib/output/modifiers/highlightCode.js
@@ -1,7 +1,35 @@
+var is = require('is');
 var Promise = require('../../utils/promise');
 var editHTMLElement = require('./editHTMLElement');
 
 /**
+    Return language for a code blocks from a list of class names
+
+    @param {Array<String>}
+    @return {String}
+*/
+function getLanguageForClass(classNames) {
+    return classNames
+        .map(function(cl) {
+            // Markdown
+            if (cl.search('lang-') === 0) {
+                return cl.slice('lang-'.length);
+            }
+
+            // Asciidoc
+            if (cl.search('language-') === 0) {
+                return cl.slice('language-'.length);
+            }
+
+            return null;
+        })
+        .find(function(cl) {
+            return Boolean(cl);
+        });
+}
+
+
+/**
     Highlight all code elements
 
     @param {Function(lang, body) -> String} highlight
@@ -11,28 +39,12 @@ var editHTMLElement = require('./editHTMLElement');
 function highlightCode(highlight, $) {
     return editHTMLElement($, 'code', function($code) {
         var classNames = ($code.attr('class') || '').split(' ');
-        var lang = classNames
-            .map(function(cl) {
-                // Markdown
-                if (cl.search('lang-') === 0) {
-                    return cl.slice('lang-'.length);
-                }
-
-                // Asciidoc
-                if (cl.search('language-') === 0) {
-                    return cl.slice('language-'.length);
-                }
-
-                return null;
-            })
-            .find(function(cl) {
-                return Boolean(cl);
-            });
+        var lang = getLanguageForClass(classNames);
         var source = $code.text();
 
         return Promise(highlight(lang, source))
         .then(function(r) {
-            if (r.html) {
+            if (is.string(r.html)) {
                 $code.html(r.html);
             } else {
                 $code.text(r.text);