如何在 map() 中將 Id 轉換成 Value ?

const data = [
  {id: 1, name: 'Sam', cityId: 1},
  {id: 2, name: 'Kevin', cityId: 2},
  {id: 3, name: 'Mike', cityId: 3},
];

let result = [];
for (let i = 0; i < data.length; i++) {
  let city = '';
  switch (data[i].cityId) {
    case 1:
      city = 'Taipei'
      break;
    case 2:
      city = 'Tokyo';
      break;
    case 3:
      city = 'Chicage';
      break;
  }

  result.push({
    id: data[i].id,
    name: data[i].name,
    cityId: data[i].cityId,
    city: city,
  });
}

console.log(result);

const data = [
  { id: 1, name: 'Sam', cityId: 1 },
  { id: 2, name: 'Kevin', cityId: 2 },
  { id: 3, name: 'Mike', cityId: 3 },
];

const cityMap = {
  1: 'Taipei',
  2: 'Tokyo',
  3: 'Chicago',
};

const result = data.map(x => ({
  ...x,
  city: cityMap[x.cityId],
}));

console.log(result);