JavaScript- recursive

Recursive process of using two prerequisites:
     1 . To recursion conditions.
    2 . Recursive end condition. 

EG: 
    var thisArr = function (ARR) {
         var new_arr = [];
         for ( var I = 0; I <arr.length; I ++ ) {
             IF (Array.isArray (ARR [I])) { 
                thisArr (ARR [I ]); 
            } the else { 
                new_arr.push (ARR [I]); 
            } 
        } 
    }; 
        
    function ladding () {
         var arr = [1,2,3,4,5,["a","b","c","d","e",["A","B","C","D","E",["FIRST","SECOND","THIRED","FOURED","FIRED"]]]];
        thisArr(arr);
        console.log(new_arr);
    }