export interface FormatNumberOptions extends Intl.NumberFormatOptions {
    /**
     * The locale(s) to used to format the number.
     *
     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl#locales_argument).
     */
    locales?: Intl.LocalesArgument;
}
export interface FormatNumberInstance {
    groupSeparator: string;
    decimalSeparator: string;
    format: (input: unknown) => string;
    parse: (input: unknown) => number | null;
}
export declare function defineNumberFormatter(options?: FormatNumberOptions): FormatNumberInstance;