diff --git a/app/assets/javascripts/merge_request_tabs.js.coffee b/app/assets/javascripts/merge_request_tabs.js.coffee
index 321feb63b0..69258be5f2 100644
--- a/app/assets/javascripts/merge_request_tabs.js.coffee
+++ b/app/assets/javascripts/merge_request_tabs.js.coffee
@@ -180,6 +180,8 @@ class @MergeRequestTabs
     $.ajax(options)
 
   diffViewMode: ->
+    # Gets diff view mode based from its ID
+    # See diff_btn helper method
     btnID = $('a[id$="-diff-btn"].active').attr('id')
     btnID.substr(0, btnID.indexOf('-'))