typescript 使用class 提示不存在属性，请问该如何处理？

Question

class Father {
    constructor(surname) {
        this.surname = surname;
    }
    say() {
        console.log('你的姓是' + this.surname);
    }
}
class Son extends Father {
    // 这样子类就继承了父类的属性和方法
}
var damao = new Son('刘');
damao.say();

上面是代码，下面图片是报错

Answer 1

typescript中变量要声明所属的数据类型，不确定类型下声明为any

class Father {
    surname: any
    constructor(surname:string) {
      this.surname = surname;
    }
    say() {
      console.log('你的姓是' + this.surname);
    }
}
class Son extends Father {
    // 这样子类就继承了父类的属性和方法
    constructor (surname:string) {
      super(surname)
    }
}
var damao = new Son('刘');
damao.say();

运行结果:

Answer 2

 
class Father {
var surname ;
    constructor(surname) {
        this.surname = surname;
    }
    say() {
        console.log('你的姓是' + this.surname);
    }
}
class Son extends Father {
    // 这样子类就继承了父类的属性和方法
}
var damao = new Son('刘');
damao.say();