i am a good javascript programmer dot .js

function prots(o, rest = []) {
   return o && (o = Object.getPrototypeOf(o)) === rest[0]
             ? rest
             : rest.unshift(o) && prots(o, rest)
}

function common(a, b) {
   return (b = prots(b)) && prots(a).filter((prot, i)=>
      prot === b[i])
}