export interface CsrfTokenObserver {
    (token: string): void;
}
/**
 * Get current request token
 *
 * @return {string|null} Current request token or null if not set
 */
export declare function getRequestToken(): string | null;
/**
 * Add an observer which is called when the CSRF token changes
 *
 * @param observer The observer
 */
export declare function onRequestTokenUpdate(observer: CsrfTokenObserver): void;