Add a localstorage.js module

(imported from commit 9f3ab248ce84ce296bb1fb918de3b2dd8cde1ded)

static/js/localstorage.js

@@ -0,0 +1,21 @@
+var localstorage = (function () {
+
+var exports = {};
+
+var warned_of_localstorage = false;
+
+exports.supported = function supports_localstorage() {
+    try {
+        return window.hasOwnProperty('localStorage') && window.localStorage !== null;
+    } catch (e) {
+        if (!warned_of_localstorage) {
+            blueslip.error("Client browser does not support local storage, will lose socket message on reload");
+            warned_of_localstorage = true;
+        }
+        return false;
+    }
+};
+
+return exports;
+
+}());

tools/jslint/check-all.js

@@ -44,6 +44,9 @@ var globals =
     // echo.js
     + ' echo'
 
+    // localstorage.js
+    + ' localstorage'
+
     // zulip.js
     + ' all_msg_list home_msg_list narrowed_msg_list current_msg_list get_updates_params'
     + ' add_messages'

zproject/settings.py

@@ -512,6 +512,7 @@ JS_SPECS = {
             'js/summary.js',
             'js/util.js',
             'js/dict.js',
+            'js/localstorage.js',
             'js/channel.js',
             'js/muting.js',
             'js/muting_ui.js',