Convert crypto/store/* to Typescript

src/indexeddb-helpers.ts

@@ -0,0 +1,50 @@
+/*
+Copyright 2019 New Vector Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+/**
+ * Check if an IndexedDB database exists. The only way to do so is to try opening it, so
+ * we do that and then delete it did not exist before.
+ *
+ * @param {Object} indexedDB The `indexedDB` interface
+ * @param {string} dbName The database name to test for
+ * @returns {boolean} Whether the database exists
+ */
+export function exists(indexedDB: IDBFactory, dbName: string): Promise<boolean> {
+    return new Promise<boolean>((resolve, reject) => {
+        let exists = true;
+        const req = indexedDB.open(dbName);
+        req.onupgradeneeded = () => {
+            // Since we did not provide an explicit version when opening, this event
+            // should only fire if the DB did not exist before at any version.
+            exists = false;
+        };
+        req.onblocked = () => reject(req.error);
+        req.onsuccess = () => {
+            const db = req.result;
+            db.close();
+            if (!exists) {
+                // The DB did not exist before, but has been created as part of this
+                // existence check. Delete it now to restore previous state. Delete can
+                // actually take a while to complete in some browsers, so don't wait for
+                // it. This won't block future open calls that a store might issue next to
+                // properly set up the DB.
+                indexedDB.deleteDatabase(dbName);
+            }
+            resolve(exists);
+        };
+        req.onerror = ev => reject(req.error);
+    });
+}