eloquent js: chapter 4: List Exercise implementation

function arrayToList(arr){
    var prevList;
    var ref;
    for(var i = arr.length - 1; i >= 0; i--){
        if(i === arr.length - 1){
            ref = null;
        }else{
            ref = prevList;
        }

        var currentList = {value: arr[i], rest: ref};
        prevList = currentList;
    }

    return prevList;
}

function listToArray(list){
    var arr = [];
    var currentObj = list;

    // loop
    while((currentObj.rest === null) || (currentObj.rest != null)){
        // console.log(currentObj.rest === null); // f, f, f, t
        arr.push(currentObj.value);

        if(currentObj.rest != null){
            currentObj = currentObj.rest;
        }else{
            break;
        }
    }

    return arr;
}

function prepend(element, list){
    return {value: element, rest: list};
}

function nth(list, index){
    var currentList = list;
    for(var i = 0; i < index; i++){
        if(currentList.rest != null){
            currentList = currentList.rest;
        }else{
            currentList.value = "undefined";
            break;
        }
    }

    return currentList.value;
}

//overload/write with a recursive version of nth

function nth(list, index){
    if(index === 0){
        return list.value;
    }else if(list.rest === null){
        return undefined;
    }else{
        return nth(list.rest, index - 1);
    }
}

// this is a broken down valid recursion example that's functioning.
function nth(list, index){
    if(index === 0){
        return index;
    }else{
        console.log(index);
        return nth(list, index - 1);
    }
}