来自array.map()的意外结果

const numbers = [1, 2, 3];
const doubled = numbers.map(num => {
  num * 2; // 没有返回值
});

console.log(doubled); // [undefined, undefined, undefined]

const numbers = [1, 2, 3];
const doubled = numbers.map(num => num * 2);

console.log(doubled); // [2, 4, 6]

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' }
];

const updatedUsers = users.map(user => {
  user.age = 30; // 直接修改了原对象
  return user;
});

console.log(users); // [{ id: 1, name: 'Alice', age: 30 }, { id: 2, name: 'Bob', age: 30 }]

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' }
];

const updatedUsers = users.map(user => ({
  ...user,
  age: 30
}));

console.log(users); // [{ id: 1, name: 'Alice' }, { id: 2, name: 'Bob' }]
console.log(updatedUsers); // [{ id: 1, name: 'Alice', age: 30 }, { id: 2, name: 'Bob', age: 30 }]