three(times(four()))

function num(N) {
  return function() {
    const VAL = N;
    let res = 0;
    if (arguments.length == 0) return VAL;
    if (arguments.length == 1) res = eval(N + arguments[0]);
    return Math.floor(res);
  };
}

one = num(1);
two = num(2);
three = num(3);
four = num(4);
five = num(5);
six = num(6);
seven = num(7);
eight = num(8);
nine = num(9);
one(add(two()));

function add(num) {
  return '+' + num;
}
function sub(num) {
  return '-' + num;
}
function mul(num) {
  return '*' + num;
}
function divBy(num) {
  return '/' + num;
}