5、类（修饰符）

public 默认修饰符

class Animal {
  public name: string;
  constructor(name: string) {
    this.name = name
  }
  run() {
    return `${this.name} is running`
  }
}
const snake = new Animal('lily')
console.log(snake.run())
snake.name = 'lucy'
console.log(snake.run())

private 修饰符：子类不可访问属性

class Animal {
  private name: string;
  constructor(name: string) {
    this.name = name
  }
  run() {
    return `${this.name} is running`
  }
}
const snake = new Animal('lily')
console.log(snake.run())
class Dog extends Animal {
  bark() {
    return `${this.name} is barking`    // 子类不可访问
  }
}

protected 修饰符：子类可以访问属性

class Animal {
  protected name: string;
  constructor(name: string) {
    this.name = name
  }
  run() {
    return `${this.name} is running`
  }
}
const snake = new Animal('lily')
console.log(snake.run())
class Dog extends Animal {
  bark() {
    return `${this.name} is barking`
  }
}

readonly 修饰符
只可读取属性，不可更改

class Animal {
  readonly name: string;
  constructor(name: string) {
    this.name = name
  }
  run() {
    return `${this.name} is running`
  }
}
const snake = new Animal('lily')
console.log(snake.run())
snake.name = 'kip'    // 报错

static 修饰符

class Animal {
  readonly name: string;
  static categoies: string[] = ['mammal', 'bird'];
  constructor(name: string) {
    this.name = name
  }
  run() {
    return `${this.name} is running`
  }
}
const snake = new Animal('lily')
console.log(snake.run())
console.log(Animal.categoies)