From 70e6076129150b5a8de3a5eef70f1f79df21b4ce Mon Sep 17 00:00:00 2001
From: Jason Leung <hangindev@gmail.com>
Date: Thu, 1 Oct 2020 12:29:19 +0800
Subject: [PATCH] Add language label only if class attribute exists.

---
 website/themes/nnja-theme-learn/static/js/learn.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/website/themes/nnja-theme-learn/static/js/learn.js b/website/themes/nnja-theme-learn/static/js/learn.js
index 48b1029..1b4da81 100644
--- a/website/themes/nnja-theme-learn/static/js/learn.js
+++ b/website/themes/nnja-theme-learn/static/js/learn.js
@@ -8,7 +8,10 @@ $("pre code").each(function (i, e) {
     var code = $(e);
     var pre = code.parent();
 
-    var language = code.attr('class').replace('language-', '');
+    var className = code.attr('class');
+    if(!className) return;
+
+    var language = className.replace('language-', '');
     var text_block = pre.text();
 
     is_python_repl = text_block.includes(">>> ");