const object1 = {name: 'Tu', hobbies: 'coding'}
createNewObjectWithES6 = (prevObj, key, value) => {
  return {
    ...prevObj,
    [key]: value
  }
}

console.log(createNewObjectWithES6(object1, 'age', 31))
// { name: 'Tu', hobbies: 'coding', age: 31 }