es2020.intl.d.ts

declare namespace Intl {

    /**
     * [BCP 47 language tag](http://tools.ietf.org/html/rfc5646) definition.
     *
     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl#locales_argument).
     *
     * [Wikipedia](https://en.wikipedia.org/wiki/IETF_language_tag).
     */
    type BCP47LanguageTag = string;

    /**
     * Unit to use in the relative time internationalized message.
     *
     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/format#Parameters).
     *
     * [Specification](https://tc39.es/ecma402/#sec-singularrelativetimeunit).
     */
    type RelativeTimeFormatUnit =
        | "year" | "years"
        | "quarter" | "quarters"
        | "month" | "months"
        | "week" | "weeks"
        | "day" | "days"
        | "hour" | "hours"
        | "minute" | "minutes"
        | "second" | "seconds"
        ;

    /**
     * The locale matching algorithm to use.
     *
     * [MDN](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Intl#Locale_negotiation).
     *
     * [Specification](https://tc39.es/ecma402/#sec-InitializeRelativeTimeFormat).
     */
    type RelativeTimeFormatLocaleMatcher = "lookup" | "best fit";

    /**
     * The format of output message.
     *
     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/RelativeTimeFormat#Parameters).
     *
     * [Specification](https://tc39.es/ecma402/#sec-InitializeRelativeTimeFormat).
     */
    type RelativeTimeFormatNumeric = "always" | "auto";

    /**
     * The length of the internationalized message.
     *
     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/RelativeTimeFormat#Parameters).
     *
     * [Specification](https://tc39.es/ecma402/#sec-InitializeRelativeTimeFormat).
     */
    type RelativeTimeFormatStyle = "long" | "short" | "narrow";

    /**
     * An object with some or all of properties of `options` parameter
     * of `Intl.RelativeTimeFormat` constructor.
     *
     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/RelativeTimeFormat#Parameters).
     *
     * [Specification](https://tc39.es/ecma402/#sec-InitializeRelativeTimeFormat).
     */
    interface RelativeTimeFormatOptions {
        localeMatcher?: RelativeTimeFormatLocaleMatcher;
        numeric?: RelativeTimeFormatNumeric;
        style?: RelativeTimeFormatStyle;
    }

    /**
     * An object with properties reflecting the locale
     * and formatting options computed during initialization
     * of the `Intel.RelativeTimeFormat` object
     *
     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/resolvedOptions#Description).
     *
     * [Specification](https://tc39.es/ecma402/#table-relativetimeformat-resolvedoptions-properties)
     */
    interface ResolvedRelativeTimeFormatOptions {
        locale: BCP47LanguageTag;
        style: RelativeTimeFormatStyle;
        numeric: RelativeTimeFormatNumeric;
        numberingSystem: string;
    }

    /**
     * An object representing the relative time format in parts
     * that can be used for custom locale-aware formatting.
     *
     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/formatToParts#Using_formatToParts).
     *
     * [Specification](https://tc39.es/ecma402/#sec-FormatRelativeTimeToParts).
     */
    interface RelativeTimeFormatPart {
        type: string;
        value: string;
        unit?: RelativeTimeFormatUnit;
    }

    interface RelativeTimeFormat {
        /**
         * Formats a value and a unit according to the locale
         * and formatting options of the given
         * [`Intl.RelativeTimeFormat`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/RelativeTimeFormat)
         * object.
         *
         * While this method automatically provides the correct plural forms,
         * the grammatical form is otherwise as neutral as possible.
         * It is the caller's responsibility to handle cut-off logic
         * such as deciding between displaying "in 7 days" or "in 1 week".
         * This API does not support relative dates involving compound units.
         * e.g "in 5 days and 4 hours".
         *
         * @param value -  Numeric value to use in the internationalized relative time message
         *
         * @param unit - [Unit](https://tc39.es/ecma402/#sec-singularrelativetimeunit)
         *  to use in the relative time internationalized message.
         *  Possible values are: `"year"`, `"quarter"`, `"month"`, `"week"`,
         *  `"day"`, `"hour"`, `"minute"`, `"second"`.
         *  Plural forms are also permitted.
         *
         * @throws `RangeError` if `unit` was given something other than `unit` possible values
         *
         * @returns Internationalized relative time message as string
         *
         * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/format).
         *
         * [Specification](https://tc39.es/ecma402/#sec-Intl.RelativeTimeFormat.prototype.format).
         */
        format(
            value: number,
            unit: RelativeTimeFormatUnit,
        ): string;

        /**
         *  A version of the format method which it returns an array of objects
         *  which represent "parts" of the object,
         *  separating the formatted number into its constituent parts
         *  and separating it from other surrounding text.
         *  These objects have two properties:
         * `type` a NumberFormat formatToParts type, and `value`,
         *  which is the String which is the component of the output.
         *  If a "part" came from NumberFormat,
         *  it will have a unit property which indicates the `unit` being formatted;
         *  literals which are part of the larger frame will not have this property.
         *
         *  @param value - Numeric value to use in the internationalized relative time message
         *
         *  @param unit - [Unit](https://tc39.es/ecma402/#sec-singularrelativetimeunit)
         *   to use in the relative time internationalized message.
         *   Possible values are: `"year"`, `"quarter"`, `"month"`, `"week"`,
         *   `"day"`, `"hour"`, `"minute"`, `"second"`.
         *   Plural forms are also permitted.
         *
         *  @throws `RangeError` if `unit` was given something other than `unit` possible values
         *
         *  @returns Array of [FormatRelativeTimeToParts](https://tc39.es/ecma402/#sec-FormatRelativeTimeToParts)
         *
         *  [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/formatToParts).
         *
         *  [Specification](https://tc39.es/ecma402/#sec-Intl.RelativeTimeFormat.prototype.formatToParts).
         */
        formatToParts(
            value: number,
            unit: RelativeTimeFormatUnit,
        ): RelativeTimeFormatPart[];

        /**
         * Provides access to the locale and options computed during initialization of this `Intl.RelativeTimeFormat` object.
         *
         * @returns A new object with properties reflecting the locale
         *  and formatting options computed during initialization
         *  of the `Intel.RelativeTimeFormat` object.
         *
         * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/resolvedOptions).
         *
         * [Specification](https://tc39.es/ecma402/#sec-intl.relativetimeformat.prototype.resolvedoptions)
         */
        resolvedOptions(): ResolvedRelativeTimeFormatOptions;
    }

    /**
     * The [`Intl.RelativeTimeFormat`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/RelativeTimeFormat)
     * object is a constructor for objects that enable language-sensitive relative time formatting.
     *
     * Part of [Intl object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl)
     * namespace and the [ECMAScript Internationalization API](https://www.ecma-international.org/publications/standards/Ecma-402.htm).
     *
     * [Compatibility](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat#Browser_compatibility).
     *
     * [Polyfills](https://github.com/tc39/proposal-intl-relative-time#polyfills).
     */
    const RelativeTimeFormat: {
        /**
         * Constructor creates [Intl.RelativeTimeFormat](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RelativeTimeFormat)
         * objects
         *
         * @param locales - A string with a [BCP 47 language tag](http://tools.ietf.org/html/rfc5646), or an array of such strings.
         *  For the general form and interpretation of the locales argument,
         *  see the [`Intl` page](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl#Locale_identification_and_negotiation).
         *
         * @param options - An [object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/RelativeTimeFormat#Parameters)
         *  with some or all of options of the formatting.
         *  An object with some or all of the following properties:
         *  - `localeMatcher` - The locale matching algorithm to use.
         *    Possible values are `"lookup"` and `"best fit"`; the default is `"best fit"`.
         *    For information about this option, see [Intl page](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Intl#Locale_negotiation).
         *  - `numeric` - The format of output message.
         *    Possible values are: `"always"` (default, e.g., `1 day ago`) or `"auto"` (e.g., `yesterday`).
         *    The `"auto"` value allows to not always have to use numeric values in the output.
         *  - `style` - The length of the internationalized message. Possible values are:
         *    `"long"` (default, e.g., in 1 month),
         *    `"short"` (e.g., in 1 mo.)
         *    or `"narrow"` (e.g., in 1 mo.). The narrow style could be similar to the short style for some locales.
         *
         * @returns [Intl.RelativeTimeFormat](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RelativeTimeFormat) object.
         *
         * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/RelativeTimeFormat).
         *
         * [Specification](https://tc39.es/ecma402/#sec-intl-relativetimeformat-constructor).
         */
        new(
            locales?: BCP47LanguageTag | BCP47LanguageTag[],
            options?: RelativeTimeFormatOptions,
        ): RelativeTimeFormat;

        /**
         * Returns an array containing those of the provided locales
         * that are supported in date and time formatting
         * without having to fall back to the runtime's default locale.
         *
         * @param locales - A string with a [BCP 47 language tag](http://tools.ietf.org/html/rfc5646), or an array of such strings.
         *  For the general form and interpretation of the locales argument,
         *  see the [`Intl` page](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl#Locale_identification_and_negotiation).
         *
         * @param options - An [object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/RelativeTimeFormat#Parameters)
         *  with some or all of options of the formatting.
         *  An object with some or all of the following properties:
         *  - `localeMatcher` - The locale matching algorithm to use.
         *    Possible values are `"lookup"` and `"best fit"`; the default is `"best fit"`.
         *    For information about this option, see [Intl page](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Intl#Locale_negotiation).
         *  - `numeric` - The format of output message.
         *    Possible values are: `"always"` (default, e.g., `1 day ago`) or `"auto"` (e.g., `yesterday`).
         *    The `"auto"` value allows to not always have to use numeric values in the output.
         *  - `style` - The length of the internationalized message. Possible values are:
         *    `"long"` (default, e.g., in 1 month),
         *    `"short"` (e.g., in 1 mo.)
         *    or `"narrow"` (e.g., in 1 mo.). The narrow style could be similar to the short style for some locales.
         *
         * @returns An array containing those of the provided locales
         *  that are supported in date and time formatting
         *  without having to fall back to the runtime's default locale.
         *
         * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/RelativeTimeFormat/supportedLocalesOf).
         *
         * [Specification](https://tc39.es/ecma402/#sec-Intl.RelativeTimeFormat.supportedLocalesOf).
         */
        supportedLocalesOf(
            locales: BCP47LanguageTag | BCP47LanguageTag[],
            options?: RelativeTimeFormatOptions,
        ): BCP47LanguageTag[];
    };

    interface NumberFormatOptions {
        compactDisplay?: string;
        notation?: string;
        signDisplay?: string;
        unit?: string;
        unitDisplay?: string;
    }

    interface ResolvedNumberFormatOptions {
        compactDisplay?: string;
        notation?: string;
        signDisplay?: string;
        unit?: string;
        unitDisplay?: string;
    }

    interface DateTimeFormatOptions {
        dateStyle?: "full" | "long" | "medium" | "short";
        timeStyle?: "full" | "long" | "medium" | "short";
        calendar?: string;
        dayPeriod?: "narrow" | "short" | "long";
        numberingSystem?: string;
        hourCycle?: "h11" | "h12" | "h23" | "h24";
        fractionalSecondDigits?: 0 | 1 | 2 | 3;
    }
}