[ynherb]

let o = {
  i: 0,
  up(x){
   x || this.i++
    return this[x || "up"].bind(this)
  },
  down(x){
  x || this.i--
  return this[x || "down"].bind(this)
},
    show(x){
      console.log(this.i)
      return this[(x =x || "show")].bind(this)
    }
};

o.up("up")("down")()()("up")()()

o.i