js json 获取key

let data = {
  "name": "John",
  "age": 30,
  "city": "New York"
};

console.log(data.name); // 输出: John
console.log(data["age"]); // 输出: 30

let keys = Object.keys(data);
console.log(keys); // 输出: ["name", "age", "city"]

for (let key in data) {
  if (data.hasOwnProperty(key)) { // 确保是对象自身的属性
    console.log(key + ": " + data[key]);
  }
}

let nestedData = {
  "user": {
    "name": "Alice",
    "details": {
      "age": 25,
      "city": "Los Angeles"
    }
  }
};

console.log(nestedData.user.details.age); // 输出: 25

let users = [
  { "name": "Bob", "age": 22 },
  { "name": "Carol", "age": 27 }
];

users.forEach(user => {
  console.log(user.name);
});

let user = {
  profile: {
    name: "Dave"
  }
};

console.log(user.profile?.name); // 输出: Dave
console.log(user.profile?.age); // 输出: undefined，不会抛出错误