class People {
  name: string;
  age: number;
  constructor(name: string, age: number) {
    this.name = name;
    this.age = age;
  }
  eat(food: string): void {
    console.log("eat", food);
  }
}
const p = new People("zhangsan", 18);
p.eat("apple");

定义了一个类，还会自动定义一个接口。

interface People {
  name: string;
  age: number;
  eat: (food: string) => void;
}