MapKeys<T>

Overview

Extracts the key type from a given map type T.

Syntax

type MapKeys<T extends Map<unknown, unknown>> =
  T extends Map<infer K, unknown> ? K : never;

• T: The map type from which to extract the key type.

Examples

const phoneBook: Map<'tomas' | 'sha', string> = new Map([
 ['tomas': '010-0000-0000'],
 ['sha': '010-1111-1111'],
])

type PhoneBookKeys = MapKeys<typeof phoneBook>; // 'tomas' | 'sha'

const hashMap: Map<string, string> = new Map([
 ['0': 'coffee'],
 ['1': 'dessert']
])

type HashMapKeys = MapKeys<typeof hashMap>; // string