public

public可以在所有位置访问，包括子类

class B {
 public   name: string
 public   age: number
    constructor(name:string,age:number) {
        this.name = name
        this.age=age
    }
}
class A extends B {
    constructor(name:string,age:number) {
        super(name,age)
        console.log(this.name) //'bbb'
        console.log(this.age) //20
    }
}
let b = new B('bbb', 20)
let a=new A('aaa',10)
 console.log(b.name) //bbb ,可以在外部访问

另外，不加修饰符的属性都是 public