diff --git a/comment/comment.js b/comment/comment.js
index e15b10bd79e..3441b9d2ec1 100644
--- a/comment/comment.js
+++ b/comment/comment.js
@@ -121,7 +121,7 @@ M.core_comment = {
                                 alert('IO FATAL');
                                 return;
                             }
-                            var data = json_decode(o.responseText);
+                            var data = Y.JSON.parse(o.responseText);
                             if (data.error) {
                                 alert(data.error);
                                 return false;
diff --git a/lib/editor/tinymce/extra/strings.php b/lib/editor/tinymce/extra/strings.php
index 17a4d5fa1a1..aa523224b52 100644
--- a/lib/editor/tinymce/extra/strings.php
+++ b/lib/editor/tinymce/extra/strings.php
@@ -86,7 +86,7 @@ foreach ($string as $key=>$value) {
 
 $lang = str_replace('_utf8', '', $lang); // use more standard language codes
 
-$output = 'tinyMCE.addI18n({'.$lang.':'.json_encode($result).'});';
+$output = 'tinyMCE.addI18n({'.$lang.':'.Y.JSON.stringify($result).'});';
 
 $lifetime = '10'; // TODO: increase later
 @header('Content-type: text/javascript; charset=utf-8');
diff --git a/lib/form/filemanager.js b/lib/form/filemanager.js
index fda643b3dd3..d1b4e69c508 100644
--- a/lib/form/filemanager.js
+++ b/lib/form/filemanager.js
@@ -89,7 +89,7 @@ YUI.add('core_filemanager', function(Y) {
                             alert('IO FATAL');
                             return;
                         }
-                        var data = json_decode(o.responseText);
+                        var data = Y.JSON.parse(o.responseText);
                         args.callback(id,data,p);
                     }
                 },
diff --git a/lib/javascript-static.js b/lib/javascript-static.js
index f75112a5571..bd12b63eef4 100644
--- a/lib/javascript-static.js
+++ b/lib/javascript-static.js
@@ -158,7 +158,8 @@ M.util.CollapsibleRegion.prototype.icon = null;
 //=== old legacy JS code, hopefully to be replaced soon by M.xx.yy and YUI3 code ===
 
 function launch_filemanager(options) {
-    Y.use('core_filemanager', function() {
+	// TODO: move to M.form_filemanager.init()
+    YUI(M.yui.loader).use('core_filemanager', function(Y) {
         var client_id = options.client_id;
         // filemangers defined in lib/form/filemanager.js
         if (!filemanagers[client_id]) {
@@ -1213,14 +1214,6 @@ function stripHTML(str) {
     return ret;
 }
 
-function json_decode(json) {
-    return Y.JSON.parse(json);
-}
-
-function json_encode(data) {
-    return Y.JSON.stringify(data);
-}
-
 /**
  * Finds all help icons on the page and initiates YUI tooltips for
  * each of them, which load a truncated version of the help's content
diff --git a/mod/chat/gui_ajax/script.js b/mod/chat/gui_ajax/script.js
index 18ac9e401e3..d4b73f8c206 100644
--- a/mod/chat/gui_ajax/script.js
+++ b/mod/chat/gui_ajax/script.js
@@ -223,7 +223,7 @@ YAHOO.moodle.chat.append_msg = function(key, msg, row) {
 
 YAHOO.moodle.chat.update_cb = {
     success: function(o){
-        var data = json_decode(o.responseText);
+        var data = Y.JSON.parse(o.responseText);
         if (!data) {
             return;
         }