import React, { ComponentState, PropsWithoutRef } from "react";
export declare function isUndefined(obj: any): obj is undefined;
export declare function usePrevious<T>(value: PropsWithoutRef<T> | ComponentState): undefined;
export declare function useMergeValue<T>(defaultStateValue: T, props?: {
    defaultValue?: T;
    value?: T;
}): [T, React.Dispatch<React.SetStateAction<T>>, T];
