/**
 * A jar of form fields to store form data by handling
 * array gracefully
 */
export declare class FormFields {
    #private;
    constructor(config: {
        convertEmptyStringsToNull: boolean;
    });
    /**
     * Add a new key/value pair. The keys with array like
     * expressions are handled properly.
     *
     * @example
     * ```
     * formfields.add('username', 'virk')
     *
     * // array
     * formfields.add('username[]', 'virk')
     * formfields.add('username[]', 'nikk')
     *
     * // Indexed keys are orderd properly
     * formfields.add('username[1]', 'virk')
     * formfields.add('username[0]', 'nikk')
     * ```
     */
    add(key: string, value: any): void;
    /**
     * Returns the copy of form fields
     */
    get(): any;
}