Added support for sessionStorage for cache.

src/__tests__/browserPlatform-test.js

@@ -134,6 +134,32 @@ describe('browserPlatform', () => {
     });
   });
 
+  describe('sessionStorage', () => {
+    const plat = browserPlatform({ bootstrap: 'sessionStorage' });
+
+    // Make sure that all of the get/set tests for the localStorage tests
+    // also work with sessionStorage.
+    it('returns null or undefined for missing value', async () => {
+      const value = await plat.localStorage.get(lsKeyPrefix + 'unused-key');
+      expect(value).not.toBe(expect.anything());
+    });
+
+    it('can get and set value', async () => {
+      const key = lsKeyPrefix + 'get-set-key';
+      await plat.localStorage.set(key, 'hello');
+      const value = await plat.localStorage.get(key);
+      expect(value).toEqual('hello');
+    });
+
+    it('can delete value', async () => {
+      const key = lsKeyPrefix + 'delete-key';
+      await plat.localStorage.set(key, 'hello');
+      await plat.localStorage.clear(key);
+      const value = plat.localStorage.get(key);
+      expect(value).not.toBe(expect.anything());
+    });
+  });
+
   describe('localStorage', () => {
     // Since we're not currently running these tests in an actual browser, this is really using a
     // mock implementation of window.localStorage, but these tests still verify that our async

src/browserPlatform.js

@@ -39,20 +39,28 @@ export default function makeBrowserPlatform(options) {
   };
 
   try {
-    if (window.localStorage) {
+    // Allow the user to specify which storage type to use. If the user specifies session storage
+    // then use that. Otherwise default to local storage. Both of these implement the same
+    // storage interface, documentation here: https://developer.mozilla.org/en-US/docs/Web/API/Storage
+    const storage =
+      ((options || {}).bootstrap || '').toUpperCase() === 'SESSIONSTORAGE'
+        ? window.sessionStorage
+        : window.localStorage;
+
+    if (storage) {
       ret.localStorage = {
         get: key =>
           new Promise(resolve => {
-            resolve(window.localStorage.getItem(key));
+            resolve(storage.getItem(key));
           }),
         set: (key, value) =>
           new Promise(resolve => {
-            window.localStorage.setItem(key, value);
+            storage.setItem(key, value);
             resolve();
           }),
         clear: key =>
           new Promise(resolve => {
-            window.localStorage.removeItem(key);
+            storage.removeItem(key);
             resolve();
           }),
       };