Record: mapowanie kluczy na typy wartości

Wprowadzenie

Podstawowa składnia Record

type Roles = Record<'admin' | 'user' | 'guest', boolean>;
const access: Roles = { admin: true, user: true, guest: false };

Record z kluczami typu string

const headers: Record<string, string> = {
  'content-type': 'application/json',
  'authorization': 'Bearer token'
};

Record dla tabel wyszukiwania

const statusLabels: Record<number, string> = {
  200: 'OK',
  404: 'Not Found',
  500: 'Server Error'
};

Implementacja Record

type Record<K extends string | number | symbol, V> = { [P in K]: V };

Record a sygnatura indeksu

// Equivalent:
type A = Record<string, number>;
type B = { [key: string]: number };

Record z wartościami unii

type Config = Record<'development' | 'staging' | 'production', { url: string; debug: boolean }>;

Częściowy Record

type OptionalConfig = Partial<Record<'debug' | 'verbose' | 'trace', boolean>>;

Tylko do odczytu Record

const CODES: Readonly<Record<string, number>> = { A: 1, B: 2 };

Record do grupowania

function groupBy<T>(items: T[], key: keyof T): Record<string, T[]> {
  return items.reduce((acc, item) => {
    const k = String(item[key]);
    (acc[k] ??= []).push(item);
    return acc;
  }, {} as Record<string, T[]>);
}

Record z kluczami enum

enum Color { Red = 'RED', Green = 'GREEN', Blue = 'BLUE' }
const hexCodes: Record<Color, string> = {
  [Color.Red]: '#FF0000',
  [Color.Green]: '#00FF00',
  [Color.Blue]: '#0000FF',
};

Szybkie sprawdzenie

Podsumowanie