使用keyof的参数泛型推断

type Person = {
  name: string;
  age: number;
};

function getProperty<T, K extends keyof T>(obj: T, key: K) {
  return obj[key];
}

const person: Person = {
  name: "John",
  age: 30,
};

const name = getProperty(person, "name"); // 类型推断为 string
const age = getProperty(person, "age"); // 类型推断为 number

type Person = {
  name: string;
  age: number;
};

function logProperties(obj: Person) {
  for (let key in obj) {
    console.log(`${key}: ${obj[key]}`);
  }
}

const person: Person = {
  name: "John",
  age: 30,
};

logProperties(person);
// 输出：
// name: John
// age: 30

type Person = {
  name: string;
  age: number;
};

function getProperty<T, K extends keyof T>(obj: T, key: K) {
  return obj[key];
}

const person: Person = {
  name: "John",
  age: 30,
};

const address = getProperty(person, "address"); // 错误，"address" 不是 Person 的属性