.locale()

Gets or sets the locale for a specific date instance.

Syntax

Get Locale

.locale(): string

Returns: string - The current locale name for this instance

Set Locale

.locale(name: string): FduInstance

Parameters:

name: string - Locale identifier (e.g., 'en', 'es', 'zh-cn')

Returns: FduInstance - New instance with the specified locale (immutable)

Examples

Get Current Locale

import { fdu } from "@pyyupsk/fdu";

const date = fdu("2024-01-15");
console.log(date.locale()); // 'en' (default)

Set Instance Locale

import { fdu, registerLocale } from "@pyyupsk/fdu";
import { es } from "@pyyupsk/fdu/locale/es";

registerLocale("es", es);

const date = fdu("2024-01-15");

// Create Spanish locale instance
const spanishDate = date.locale("es");

spanishDate.format("MMMM DD, YYYY");
// 'enero 15, 2024'

// Original unchanged
date.format("MMMM DD, YYYY");
// 'January 15, 2024'

Chaining with Locale

const date = fdu("2024-01-15")
  .locale("es")
  .add(1, "month")
  .format("dddd, D [de] MMMM");
// 'jueves, 15 de febrero'

Common Patterns

Switch Locale Temporarily

const date = fdu("2024-01-15");

// Format in different locales
const english = date.format("MMMM"); // 'January'
const spanish = date.locale("es").format("MMMM"); // 'enero'
const french = date.locale("fr").format("MMMM"); // 'janvier'

// Original instance unchanged
console.log(date.locale()); // 'en'

Multi-language Display

const date = fdu("2024-01-15");

const translations = {
  en: date.format("MMMM DD, YYYY"),
  es: date.locale("es").format("D [de] MMMM [de] YYYY"),
  fr: date.locale("fr").format("D MMMM YYYY"),
  de: date.locale("de").format("D. MMMM YYYY"),
};

console.log(translations);
// {
//   en: 'January 15, 2024',
//   es: '15 de enero de 2024',
//   fr: '15 janvier 2024',
//   de: '15. Januar 2024'
// }

Preserve Locale Through Operations

const spanishDate = fdu("2024-01-15").locale("es");

// Locale is preserved through operations
const future = spanishDate.add(1, "month").add(5, "day");

future.format("dddd, D [de] MMMM");
// 'martes, 20 de febrero' (still in Spanish)

Conditional Locale

function formatDateForUser(date: FduInstance, userLocale: string) {
  return date.locale(userLocale).format("LL");
}

const date = fdu("2024-01-15");

formatDateForUser(date, "en"); // 'January 15, 2024'
formatDateForUser(date, "es"); // '15 de enero de 2024'
formatDateForUser(date, "fr"); // '15 janvier 2024'

Immutability

The .locale() method returns a new instance and never modifies the original:

const original = fdu("2024-01-15");
const spanish = original.locale("es");

original.locale(); // 'en' (unchanged)
spanish.locale(); // 'es'