Small cleanups.

Author: cpojer

packages/jest-environment-node/src/index.ts

@@ -277,8 +277,8 @@ class GlobalProxy implements ProxyHandler<typeof globalThis> {
       ...this.leftovers,
     ]) {
       /*
-       * react-native invoke its custom `performance` property after env teardown.
-       * its setup file should use `protectProperties` to prevent this.
+       * React Native's test setup invokes their custom `performance` property after env teardown.
+       * Once they start using `protectProperties`, we can get rid of this.
        */
       if (property !== 'performance') {
         deleteProperties(value);

packages/jest-util/src/garbage-collection-utils.ts

@@ -50,5 +50,10 @@ export function protectProperties<T extends object>(
  * @param value The given value.
  */
 export function canDeleteProperties(value: unknown): value is object {
-  return value !== null && ['object', 'function'].includes(typeof value);
+  if (value !== null) {
+    const type = typeof value;
+    return type === 'object' || type === 'function';
+  }
+
+  return false;
 }