knowledge thinker

App.js in raect   import   React , {  useState ,  useRef ,  useEffect  }  from   "react" ; import   Form   from   "./components/Form" ; import   FilterButton   from   "./components/FilterButton" ; import   Todo   from   "./components/Todo" ; import  {  nanoid  }  from   "nanoid" ; function   usePrevious ( value ) {    const   ref  =  useRef ();    useEffect (()  =>  {      ref . current  =  value ;   });    return   ref . current ; } const   FILTER_MAP  = {    All :  ()  =>   true ,    Active :   task   =>  ! task . completed ,    Completed :   task   =>   task . completed }; const   FILTER_NAMES  =  Object . keys ( FILTER_MAP ); function   App (...