/**
 * A collection of form fields that stores form data while handling
 * arrays gracefully
 */
export declare class FormFields {
    #private;
    /**
     * Creates a new FormFields instance for collecting form data.
     *
     * @param normalizer - Optional normalizer function to process string values
     */
    constructor(normalizer?: (value: string) => string | null);
    /**
     * Add a new key/value pair. The keys with array-like
     * expressions are handled properly.
     *
     * @param key - The field name, can include array notation
     * @param value - The field value
     *
     * @example
     * ```
     * formfields.add('username', 'virk')
     *
     * // array
     * formfields.add('username[]', 'virk')
     * formfields.add('username[]', 'nikk')
     *
     * // Indexed keys are ordered properly
     * formfields.add('username[1]', 'virk')
     * formfields.add('username[0]', 'nikk')
     * ```
     */
    add(key: string, value: any): void;
    /**
     * Returns the collected form fields as an object.
     *
     * @example
     * ```ts
     * const fields = new FormFields()
     * fields.add('username', 'virk')
     * fields.add('tags[]', 'node')
     * fields.add('tags[]', 'typescript')
     *
     * console.log(fields.get())
     * // { username: 'virk', tags: ['node', 'typescript'] }
     * ```
     */
    get(): any;
}