有人能帮忙解释一下这段 js 的打印结果吗,问了几次 gpt 都是错误的, - V2EX
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rookiemaster
  •  
  •   rookiemaster Sep 3, 2024 3307 views
    This topic created in 601 days ago, the information mentioned may be changed or developed.
    class A { } class B extends A{ } let b = new B() console.log( b.__proto__) 

    打印结果是A{}, 不是很能理解它的含义是什么, b.__proto___不是等于 B.prototype 吗

    11 replies    2024-09-04 10:36:00 +08:00
    USDT
        1
    USDT  
       Sep 3, 2024
    对呀。。B.prototype 就是 A 啊,你 console.log 一下 B.prototype 就知道了
    zephyru
        3
    zephyru  
       Sep 3, 2024
    prototype 不就是像上找一层么?还有什么别的解释?你 new 个 A 试试,在拿 prototype 估计就是空对象了 __proto___ 这个也是
    newaccount
        4
    newaccount  
       Sep 3, 2024
    你看看 firefox 下是不是你认为的结果
    rabbbit
        5
    rabbbit  
       Sep 3, 2024
    B.prototype.__proto__ === A.prototype
    daolanfler
        6
    daolanfler  
       Sep 3, 2024
    B.prototype instanceof A // true
    B.prototype.__proto__ === A.prototype // true
    A.prototype instanceof Object // true

    const a = new A()
    chrome dev console 里面也是 a 也是 A{} 这种形式展示的
    rookiemaster
        7
    rookiemaster  
    OP
       Sep 3, 2024
    谢谢各位,清晰了
    lyxxxh2
        8
    lyxxxh2  
       Sep 3, 2024   1
    刚解决了个 bug 。
    基类:
    def init():
    self.cOnfig= Config().config
    self.config.update(self.get_config())

    多个类继承基,a 类总是被 b 类改变。
    debug 半天找不到问题。
    又怀疑基类变量的共享,但变量也不在基类啊。
    最后想起... Config()特码的是单例啊。
    mizuki9
        9
    mizuki9  
       Sep 3, 2024 via Android
    运行了一下,打印出来不是 B{}吗?
    AV1
        10
    AV1  
       Sep 3, 2024
    对的没错,b.__proto___ 和 B.prototype 都是 A 的实例。

    Object.getPrototypeOf(b) === B.prototype
    > true

    B.prototype instanceof A
    > true
    guiyumin
        11
    guiyumin  
       Sep 4, 2024
    恕我直言,这有意义吗
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