protected

protected是受保护的类型属性，它只能在当前类和当前类的子类中使用，**其他地方无法使用**

 复制代码
class B {
 protected  name: string
   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) //访问正常
        console.log(this.age)  //访问正常
    }
}
let b = new B('bbb', 10)
let a = new A('aaa', 20)
console.log(a.age)
    //age 打印正常，因为是默认ppublic
console.log(a.name)
  //  a.name 报错，因为在外部，