How to relate the conditional if and switch at the same time

function add(a, b) {
  if (a > b) {
    return a + b;
  } else {
    switch (a) {
      case 1:
        return a + b;
      case 2:
        return a - b;
      case 3:
        return a * b;
      default:
        return a / b;
    }
  }
}