A LISP inspired linked list in Javascript

linkedList.js

const nil = {}

function isNil(p){
    return p === nil
}

function makePair(a, b){
    return  {head: a, tail: b}
}

function head(p){
    return p.head
}

function tail(p){
    return p.tail
}

function array_to_list(args){
    if(args.length === 0)
        return nil
    else
        return makePair(args[0], array_to_list(args.slice(1)))
}

function append(list, val){
    if(isNil(list))
        return makePair(val, nil)
    else
        return makePair(head(list), append(tail(list), val))
}

function remove(list, val){
    if(isNil(list))
        return nil
    else if(head(list) === val)
        return tail(list)
    else
        return makePair(head(list), remove(tail(list), val))
}

function list_to_string(list){
    function helper(lst, string){
        if(isNil(lst))
            return string + ')'
        else if(isNil(tail(lst)))
            return string + head(lst) + ')'
        else
            return helper(tail(lst), string + head(lst) + ' ')
    }
    return helper(list, '(')
}

function map(func, list){
    if(isNil(list))
        return nil
    else
        return makePair(func(head(list)), map(func, tail(list)))
}

function accumulate(func, list, initial){
    if(isNil(list))
        return initial
    else
        return accumulate(func, tail(list), func(initial, head(list)))
}

function square(x){
    return x*x
}

function sum(a, b){
    return a + b
}

function test(){
    var x = [1,2,3]
    console.log(x)
    x = array_to_list(x)
    console.log(x)
    console.log(list_to_string(x))
    x = remove(x, 2)
    console.log(list_to_string(x))
    x = append(x, 5)
    console.log(list_to_string(x))
    x = map(square, x)
    console.log(list_to_string(x))
    console.log(accumulate(sum, x, 0))
}

test()