js class定义类，私有属性，类继承，子类访问父类的方法，重写父类的方法

1.使用#定义私有属性

2.使用extends实现类继承

3.使用子类使用super访问父类的方法

4.子类可以重新父类的方法

      class People {
        #hisroy = []
        getHistroy() {
          return [...this.#hisroy]
        }
        addHisroy(message) {
          this.#hisroy.push({
            role: 'user',
            message,
          })
          this.addHisroy2(message)
        }
        addHisroy2(message) {
          this.#hisroy.push({
            role: 'robot',
            message: 'Robot:' + message,
          })
        }
        addHisroy3(message) {
          this.#hisroy.push({
            role: 'user',
            message,
          })
        }
        clearHistory() {
          this.#hisroy = []
        }
      }
      class Student extends People {
        addHisroy(message) {
          if (message.includes('weather')) {
            super.addHisroy3(message)
            super.addHisroy2('天气晴朗')
          } else {
            super.addHisroy(message)
          }
        }
      }
      let p1 = new People()
      p1.addHisroy('hello')
      console.log(p1.getHistroy())
      p1.clearHistory()
      console.log(p1.getHistroy())

      let t1 = new Student()
      t1.addHisroy('hello')
      console.log(t1.getHistroy())
      t1.addHisroy('what is the weather?')
      console.log(t1.getHistroy())
      t1.clearHistory()
      console.log(t1.getHistroy())

https://www.kancloud.cn/fundebug/fundebug-blog/1039647

https://jamie.build/javascripts-new-private-class-fields.html