Adjust isUndefined check (#1546)

CHANGELOG.md

@@ -1,5 +1,12 @@
 # CHANGELOG
 
+## master
+
+Changes:
+
+- Adjust `isUndefined` check (local variable available)
+
+
 ## 9.5.1 Jun 18, 2022
 
 Contributed:

packages/util/src/is/undefined.spec.ts

@@ -1,6 +1,7 @@
 // Copyright 2017-2022 @polkadot/util authors & contributors
 // SPDX-License-Identifier: Apache-2.0
 
+import { performance } from '../test/performance';
 import { isUndefined } from '.';
 
 describe('isUndefined', (): void => {
@@ -15,4 +16,6 @@ describe('isUndefined', (): void => {
       isUndefined(null)
     ).toEqual(false);
   });
+
+  performance('isUndefined', 10_000_000, [[null]], isUndefined);
 });

packages/util/src/is/undefined.ts

@@ -17,5 +17,5 @@
  */
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 export function isUndefined (value?: unknown): value is undefined {
-  return typeof value === 'undefined';
+  return value === undefined;
 }