Type-safe definitions of `Object.keys`, `Object.entries`, and `Object.values`: `objectKeys`, `objectEntries`, and `objectValues`

type-safe-object-functions.ts

/**
 * ObjectType matches any "regular" object.
 *
 * For example:
 *   > {} satisfies ObjectType
 *   > { a: 1, b: 2 } satisfies ObjectType
 *   > [] satisfies ObjectType
 *   > null satisfies ObjectType
 *   TypeError: 'null' does not satisfy 'ObjectType'.
 *   > undefined satisfies ObjectType
 *   TypeError: 'undefined' does not satisfy 'ObjectType'.
 *   > 1 satisfies ObjectType
 *   TypeError: 'number' does not satisfy 'ObjectType'.
 *   > 'string' satisfies ObjectType
 *   TypeError: 'string' does not satisfy 'ObjectType'.
 *   > true satisfies ObjectType
 *   TypeError: 'boolean' does not satisfy 'ObjectType'.
 */
export type ObjectType = Record<PropertyKey, any>;

// Source: https://github.com/sindresorhus/ts-extras/blob/main/source/object-keys.ts
type ObjectKeys<T> = `${Exclude<keyof T, symbol>}`;
  
// Source: https://dev.to/harry0000/a-bit-convenient-typescript-type-definitions-for-objectentries-d6g
type TupleEntry<T extends readonly unknown[], I extends unknown[] = [], R = never> = T extends
  readonly [infer Head, ...infer Tail] ? TupleEntry<Tail, [...I, unknown], R | [`${I['length']}`, Head]>
  : R;

type ObjectEntry<T> = T extends object
  ? { [K in keyof T]: [K, Required<T>[K]] }[keyof T] extends infer E
    ? E extends [infer K, infer V] ? K extends string | number ? [`${K}`, V]
      : never
    : never
  : never
  : never;

type Entry<T> = T extends readonly [unknown, ...unknown[]] ? TupleEntry<T>
  : T extends ReadonlyArray<infer U> ? [`${number}`, U]
  : ObjectEntry<T>;


/**
 * A strongly-typed version of `Object.keys()`.
 */
export const objectKeys = Object.keys as <T extends ObjectType>(value: T) => Array<ObjectKeys<T>>;

/**
 * A strongly-typed version of `Object.entries()`.
 */
export const objectEntries = Object.entries as <T extends ObjectType>(value: T) => ReadonlyArray<Entry<T>>;

/**
 * A strongly-typed version of `Object.values()`.
 */
export const objectValues = Object.values as <T extends ObjectType, K extends keyof T>(value: T) => ReadonlyArray<T[K]>;