Add randomString factored out from client secret

src/client.js

@@ -50,6 +50,7 @@ import Crypto from './crypto';
 import { isCryptoAvailable } from './crypto';
 import { encodeRecoveryKey, decodeRecoveryKey } from './crypto/recoverykey';
 import { keyForNewBackup, keyForExistingBackup } from './crypto/backup_password';
+import { randomString } from './randomstring';
 
 // Disable warnings for now: we use deprecated bluebird functions
 // and need to migrate, but they spam the console with warnings.
@@ -3862,14 +3863,7 @@ MatrixClient.prototype.getEventMapper = function() {
  * @return {string} A new client secret
  */
 MatrixClient.prototype.generateClientSecret = function() {
-    let ret = "";
-    const chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
-
-    for (let i = 0; i < 32; i++) {
-        ret += chars.charAt(Math.floor(Math.random() * chars.length));
-    }
-
-    return ret;
+    return randomString(32);
 };
 
 /** */

src/randomstring.js

@@ -0,0 +1,26 @@
+/*
+Copyright 2018 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.
+*/
+
+export function randomString(len) {
+    let ret = "";
+    const chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+
+    for (let i = 0; i < len; ++i) {
+        ret += chars.charAt(Math.floor(Math.random() * chars.length));
+    }
+
+    return ret;
+}