JS对象如何声明_JavaScript对象声明与属性访问详细指南

const person = {
  name: 'Alice',
  age: 25,
  city: 'Beijing'
};

const person = new Object();
person.name = 'Bob';
person.age = 30;

function Person(name, age) {
  this.name = name;
  this.age = age;
}
const p1 = new Person('Charlie', 35);

class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
}
const p2 = new Person('Diana', 28);

console.log(person.name); // 输出: Alice
person.age = 26; // 修改属性

console.log(person['city']); // 输出: Beijing
const key = 'age';
console.log(person[key]); // 输出: 25

// 属性名含空格或连字符
const user = {
  'full-name': 'John Doe',
  'phone number': '123-456-7890'
};
console.log(user['full-name']); // 必须用方括号

person.job = 'Engineer';
person['isStudent'] = false;

delete person.city;
delete person['isStudent'];

const address = user?.address?.street;
// 如果 user 或 address 为 null/undefined，不会报错，返回 undefined

const userName = person.name ?? 'Unknown';