Localized date and time display
Render dates and times according to a user's language and regional conventions.
JavaScript · Module
Intl
Intl is the namespace for JavaScript's ECMAScript Internationalization API. Its constructors and utilities provide locale-sensitive comparison, formatting, and other language-aware operations.
How it works
Intl is a namespace object for the ECMAScript Internationalization API. Its constructors and static utilities support locale-sensitive comparison, number formatting, date and time formatting, and other language-aware operations; it is used through its static members and constructors rather than called or instantiated itself.
Parameters
| Name | Type | Description |
|---|---|---|
locales | string | Intl.Locale | string[] | undefined | Preferred locale identifier, an Intl.Locale object, a locale list, or undefined to use the default locale. |
options | object | undefined | An object whose available properties depend on the constructor or function using it. |
Key points
- The namespace covers multiple internationalization features rather than one formatting operation.
- Use its exposed static members directly; the namespace does not have instance methods.
- Locale input selects the linguistic and regional conventions for an operation.
- Locale negotiation chooses the best supported match instead of requiring every requested locale to be available.
- A single locale may be represented by a BCP 47-style identifier or an
Intl.Localeinstance. - Multiple preferences can be supplied so the runtime can try fallback locales.
Common mistakes
- Do not use
new Intl(); the namespace itself cannot be constructed. - Calling
Intl()or applyingnewtoIntlthrows instead of performing an operation.
Example: Locale-sensitive date and currency formatting
const locale = navigator.language;
const date = new Intl.DateTimeFormat(locale, {
dateStyle: "medium",
}).format(new Date());
const amount = new Intl.NumberFormat(locale, {
style: "currency",
currency: "USD",
}).format(1234.5);
console.log(`${date}: ${amount}`);The formatters use the browser's preferred locale to produce localized date and currency strings.
When to use it
Localized numeric output
Format prices, measurements, and quantities using locale-appropriate separators and patterns.
Locale-aware text comparison
Compare or sort user-facing text according to language-specific collation rules.
Locale negotiation and locale utilities
Inspect or normalize locale preferences before selecting an internationalized UI behavior.
Interview questions
QWhat is Intl in JavaScript?
Intl is a namespace object that groups the ECMAScript Internationalization API. It provides constructors and shared functionality for locale-sensitive tasks such as string comparison, number formatting, and date and time formatting.
Follow-up: How are requested locales handled? Constructors and language-sensitive methods negotiate the requested locale list against supported locales, using the localeMatcher option when applicable.
QCan Intl be called or instantiated directly?
Intl itself is not constructible or callable, and its members are static. Individual API objects, such as Intl.NumberFormat, are created through their own constructors.
Follow-up: What happens when no locale is supplied? The implementation uses its default locale, while an explicitly supplied locale or locale list expresses the preferred language or region.
QWhat are the common locales and options arguments?
The locales argument identifies the preferred locale for an operation. It can be omitted, supplied as one locale identifier or Intl.Locale object, or supplied as a list of locales; the implementation selects the closest supported locale.
Follow-up: What does options do? It is an object whose properties vary by constructor or function and can control formatting or locale negotiation behavior.
Related
Intl.CollatorIntl.DateTimeFormatIntl.DisplayNamesIntl.ListFormatIntl.LocaleIntl.NumberFormatIntl.PluralRulesIntl.RelativeTimeFormat