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String Methods

toISOString()​

Returns a date as a string value in ISO format (UTC).

Signature​

toISOString(): ISODateTimeString

Return Type​

ISODateTimeString - Standard ISO 8601 string

Notes​

  • Always returns UTC time
  • Consistent with native Date behavior

Example​

new Chronos('2025-01-01T00:00:00-05:00').toISOString();
// "2025-01-01T05:00:00.000Z"

toLocalISOString()​

Returns ISO time string in appropriate time zone with offset.

Signature​

toLocalISOString(): ISOTimeString

Return Type​

ISOTimeString - ISO string with time zone offset

Notes​

Example​

new Chronos('2025-01-01T00:00:00-05:00').toLocalISOString();
// "2025-01-01T00:00:00.000-05:00"

toLocaleString()​

Wrapper over native Date object's toLocaleString method with improved type system.

Signature​

toLocaleString(locales?: LocalesArguments, options?: DateTimeFormatOptions): string

Parameters​

  • locale: Locale string(s)
  • options: Enhanced Intl.DateTimeFormat options

Type Definitions​

/** `BCP47` locale string or `Intl.Locale` object that contain one or more language or locale tags */
type $LocalArguments = LooseLiteral<LocaleCode | Split<LocaleCode, '-'>[0]> | Intl.Locale;

/** `BCP47` locale string, array of locale strings, `Intl.Locale` object, or array of `Intl.Locale` objects that contain one or more language or locale tags. */
type LocalesArguments = $LocalArguments | $LocalArguments[];

/** Locale calendars supported by `Intl` API */
type LocaleCalendar = 'buddhist' |'chinese' | 'coptic' | 'ethiopic' | 'gregory' | 'hebrew' | 'indian' | 'islamic' | ... ;

/** Locale numbering systems supported by `Intl` API */
type NumberingSystem = 'adlm' | 'ahom' | 'arab' | 'arabext' | 'bali' | 'beng' | 'bhks' | 'brah' | 'cakm' | 'cham' | ... ;

/** Extends `Intl.DateTimeFormatOptions` with improved type system. */
interface DateTimeFormatOptions extends Intl.DateTimeFormatOptions {
 /** Time zone identifier to use. */
 timeZone?: $TimeZoneIdentifier;
 /** Locale calendar system to use. */
 calendar?: LocaleCalendar;
 /** Locale numbering system to use. */
 numberingSystem?: NumberingSystem;
}

Return Type​

string - Localized date string

Notes​

Example​

new Chronos('2025-01-15').toLocaleString('en-US', { 
  weekday: 'long', 
  year: 'numeric', 
  month: 'long', 
  day: 'numeric' 
});
// "Wednesday, January 15, 2025"

toString()​

Returns a string representation of a date.

Signature​

toString(): string

Return Type​

string - Date string

Notes​

  • Returns localized string representation.
  • Includes timezone information when relevant.

Example​

new Chronos('2025-01-15').toString();
// "Sun Jan 15 2025 00:00:00 GMT-0500 (Eastern Standard Time)"

toJSON()​

Enables JSON.stringify to show readable output. Calls toLocalISOString method.

Signature​

toJSON(): string

Return Type​

string - ISO string

Notes​

  • Used by JSON.stringify()
  • Same as toLocalISOString()

Example​

JSON.stringify({ date: new Chronos('2025-01-15') });
// '{"date":"2025-01-15T06:00:00.000+06:00"}'

inspect()​

Returns a debug-friendly string for console.log or util.inspect.

Signature​

inspect(): string

Return Type​

string - Debug-friendly string

Notes​

  • Used by Node.js util.inspect
  • Includes Chronos prefix

Example​

new Chronos('2025-01-15').inspect();
// "[Chronos 2025-01-15T00:00:00.000-05:00]"