RN-specific getRandomValues (no node crypto) (#747)

* RN-specific getRandomValues (no node crypto)

* Use polyfilled as available

* === object

packages/x-textdecoder/src/browser.ts

@@ -1,17 +1,8 @@
 // Copyright 2017-2020 @polkadot/x-textencoder authors & contributors
 // SPDX-License-Identifier: Apache-2.0
 
-export default typeof TextDecoder === 'undefined'
-  ? class {
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars,no-useless-constructor
-    constructor (_: 'utf-8') {
-      // nothing
-    }
+import Fallback from './fallback';
 
-    decode (value: Uint8Array): string {
-      return value.reduce((str, code): string => {
-        return str + String.fromCharCode(code);
-      }, '');
-    }
-  }
+export default typeof TextDecoder === 'undefined'
+  ? Fallback
   : TextDecoder;

packages/x-textdecoder/src/fallback.ts

@@ -0,0 +1,15 @@
+// Copyright 2017-2020 @polkadot/x-textencoder authors & contributors
+// SPDX-License-Identifier: Apache-2.0
+
+export default class TextDecoder {
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars,no-useless-constructor
+  constructor (_: 'utf-8') {
+    // nothing
+  }
+
+  decode (value: Uint8Array): string {
+    return value.reduce((str, code): string => {
+      return str + String.fromCharCode(code);
+    }, '');
+  }
+}