/**
 * Carefully adds a token to a space-separated attribute
 * Similar to classList, but for any attribute.
 * @see https://developer.mozilla.org/en-US/docs/Web/API/DOMTokenList/add
 */
export declare function add(element: Element, attr: string, token: string): void;
/**
 * Carefully removes a token from a space-separated attribute.
 * Similar to classList, but for any attribute.
 * @see https://developer.mozilla.org/en-US/docs/Web/API/DOMTokenList/remove
 */
export declare function remove(element: Element, attr: string, token: string): void;