节点.js基于其值返回对象键

在 节点8.10

例子

// I do not like this solution, there is a 2 line body
// `c` may be undefined or a string (for example)
const f = (a, b, c) => {
  if (c) return ({ a, b, c });
  else return { a, b }
}

c 根据其价值包括或排除? 我希望这样:

// I expect this kind of solution.
const f = (a, b, c) => ({ a, b, ___????___ })