const obj = {
  name: 'Marco',
  lastName: 'Ruben'
};

for (let i in obj) {
  console.log(i); // 'name', 'lastName'
}

for (let i of obj) {
  console.log(i); // obj[Symbol.iterator] is not a function
}


const obj1 = ['uno', 'dos'];

for (let i in obj1) {
  console.log(i); // 0, 1
  console.log(obj1[i]); // 'uno', 'dos'
}

for (let i of obj1) {
  console.log(i); // 'uno', 'dos'
}