proto-typeof.js

function typeOf (val) {
  let typeDef = typeof val
  console.log('init:', typeDef)
  if (typeDef === 'object' || typeDef === 'function') {
    console.log('obj/func:', typeDef)
    typeDef = Object.prototype.toString.call(val)
    typeDef = typeDef.substring(8, typeDef.length - 1)
  }

  if (typeDef === 'Object' || typeDef === 'Array') {
    console.log('Obj/Arr:', typeDef)
    typeDef = Object.getPrototypeOf(val).constructor.name
  }

  return typeDef
}

class Klass extends Array { constructor() { super() } }
class Qlass extends Klass { constructor() { super() } }
class Strang extends String { constructor() { super() } }

console.log(typeOf(null))
console.log(typeOf(async function () {}))
console.log(typeOf(function () {}))
console.log(typeOf(new Klass()))
console.log(typeOf(new Qlass()))
console.log(typeOf(new Strang()))