成员修饰符

public 公共的

class Animal {
    public name: string;
    public constructor(theName: string) { 
        this.name = theName; 
    }
    public move(distanceInMeters: number) {
        console.log(`${this.name} moved ${distanceInMeters}m.`);
    }
}

private 私有的

• 不能被外部访问，只能在类的内部访问使用
  - 私有成员不会被继承
  

class Person {
  public name: string;
  public age: number = 18;
  private type: string = 'human'
  public constructor (name:string, age:number) {
    this.name = name
    this.age = age
  }
}

protected 受保护的

• 和 private 类似，但是可以被继承
  

class Person {
    protected name: string;
    constructor(name: string) { 
        this.name = name; 
    }
}
class Employee extends Person {
    private department: string;
    constructor(name: string, department: string) {
        super(name)
        this.department = department;
    }
    public getElevatorPitch() {
        return `Hello, my name is ${this.name} and I work in ${this.department}.`;
    }
}
let howard = new Employee("Howard", "Sales");
console.log(howard.getElevatorPitch());
console.log(howard.name); // 错误

注意，我们不能在 Person类外使用 name，但是我们仍然可以通过 Employee类的实例方法访问，因为Employee是由 Person派生而来的。