move keysOf into a new utilities file

source/index.ts

@@ -11,6 +11,7 @@ import type {
 	WeakRef,
 	Whitespace,
 } from './types.js';
+import {keysOf} from './utilities.js';
 
 // From type-fest.
 type ExtractFromGlobalConstructors<Name extends string> =
@@ -1124,10 +1125,6 @@ const methodTypeMap = {
 	isWhitespaceString: 'whitespace string',
 } as const;
 
-export function keysOf<T extends Record<PropertyKey, unknown>>(value: T): Array<keyof T> {
-	return Object.keys(value) as Array<keyof T>;
-}
-
 type IsMethodName = keyof typeof methodTypeMap;
 const isMethodNames: IsMethodName[] = keysOf(methodTypeMap);
 

source/utilities.ts

@@ -0,0 +1,3 @@
+export function keysOf<T extends Record<PropertyKey, unknown>>(value: T): Array<keyof T> {
+	return Object.keys(value) as Array<keyof T>;
+}

test/test.ts

@@ -12,13 +12,13 @@ import {expectTypeOf} from 'expect-type';
 import ZenObservable from 'zen-observable';
 import is, {
 	assert,
-	keysOf,
 	type AssertionTypeDescription,
 	type Predicate,
 	type Primitive,
 	type TypedArray,
 	type TypeName,
 } from '../source/index.js';
+import {keysOf} from '../source/utilities.js';
 
 class PromiseSubclassFixture<T> extends Promise<T> {}
 class ErrorSubclassFixture extends Error {}