Handle case if localStorage is not supported by the browser

For example, if LS is disabled by browser

Author: Hengjie

app/scripts/ng-xdLocalStorage.js

@@ -29,9 +29,15 @@ angular.module('xdLocalStorage', [])
     return {
       init: function (options) {
         var defer = $q.defer();
-        options.initCallback = function () {
-          apiReady.resolve();
-          defer.resolve();
+        options.initCallback = function (localStorageSupported) {
+          if (localStorageSupported) {
+            apiReady.resolve();
+            defer.resolve();
+          } else {
+            apiReady.reject();
+            defer.reject();
+            console.warn('localStorage not supported in iframe');
+          }
         };
         xdLocalStorage.init(options);
         return defer.promise;

app/scripts/xdLocalStorage.js

@@ -8,7 +8,7 @@ window.xdLocalStorage = window.xdLocalStorage || (function () {
   var options = {
     iframeId: 'cross-domain-iframe',
     iframeUrl: undefined,
-    initCallback: function () {}
+    initCallback: function (localStorageSupported) {}
   };
   var requestId = -1;
   var iframe;
@@ -33,7 +33,7 @@ window.xdLocalStorage = window.xdLocalStorage || (function () {
     if (data && data.namespace === MESSAGE_NAMESPACE) {
       if (data.id === 'iframe-ready') {
         iframeReady = true;
-        options.initCallback();
+        options.initCallback(data.localStorageSupported);
       } else {
         applyCallback(data);
       }

app/scripts/xdLocalStoragePostMessageApi.js

@@ -10,6 +10,28 @@
   var allowedOriginsAttr = (postApi && postApi.getAttribute("accepted-origins")) || '';
   var allowedOrigins = allowedOriginsAttr.split(',');
 
+  // Checks the browser to see if local storage is supported
+  var browserSupportsLocalStorage = (function () {
+    try {
+      var supported = ('localStorage' in window && window['localStorage'] !== null);
+
+      // When Safari (OS X or iOS) is in private browsing mode, it appears as though localStorage
+      // is available, but trying to call .setItem throws an exception.
+      //
+      // "QUOTA_EXCEEDED_ERR: DOM Exception 22: An attempt was made to add something to storage
+      // that exceeded the quota."
+      if (supported) {
+        var key = '__' + Math.round(Math.random() * 1e7);
+        localStorage.setItem(key, '');
+        localStorage.removeItem(key);
+      }
+
+      return supported;
+    } catch (e) {
+      return false;
+    }
+  }());
+
   // Verify the sender's origin has been whitelisted
   function isOriginAllowed(origin) {
     if (allowedOrigins.length === 1 && (allowedOrigins[0] === '*' || allowedOrigins[0] === '')) {
@@ -103,7 +125,8 @@
   function sendOnLoad() {
     var data = {
       namespace: MESSAGE_NAMESPACE,
-      id: 'iframe-ready'
+      id: 'iframe-ready',
+      localStorageSupported: browserSupportsLocalStorage
     };
     parent.postMessage(JSON.stringify(data), '*');
   }