js json 取key

let jsonObject = {
  "name": "Alice",
  "age": 30,
  "city": "New York"
};

let name = jsonObject.name; // "Alice"

let age = jsonObject["age"]; // 30

// 使用变量作为键名
let key = "city";
let city = jsonObject[key]; // "New York"

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

// 使用Object.keys()方法
Object.keys(jsonObject).forEach(key => {
  console.log(key + ": " + jsonObject[key]);
});

let jsonObject = {
  "first-name": "Bob",
  "last name": "Smith"
};

let firstName = jsonObject["first-name"]; // "Bob"
let lastName = jsonObject["last name"]; // "Smith"

let country = jsonObject.country; // undefined
if (country === undefined) {
  console.log("Country information is missing.");
}

let jsonString = '{"name":"Charlie","age":25}';
let jsonObject = JSON.parse(jsonString);
let name = jsonObject.name; // "Charlie"