如果为空，则初始化解构属性

const user = {
  name: 'Alice',
  age: 25,
};

const { name, age, gender = 'unknown' } = user;

console.log(name);    // 输出: Alice
console.log(age);     // 输出: 25
console.log(gender);  // 输出: unknown

const numbers = [1, 2];

const [first, second, third = 0] = numbers;

console.log(first);   // 输出: 1
console.log(second);  // 输出: 2
console.log(third);   // 输出: 0

const user = {
  name: 'Alice',
};

const { name, age = 'unknown' } = user;

console.log(name);   // 输出: Alice
console.log(age);    // 输出: unknown

const numbers = [1, 2];

const [first, second, ...rest = []] = numbers;

console.log(first);   // 输出: 1
console.log(second);  // 输出: 2
console.log(rest);    // 输出: []