手写了下 js 类的继承,请教个 js 问题 - V2EX
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gaocc

手写了下 js 类的继承,请教个 js 问题

  •  1
     
  •   gaocc Jan 10, 2022 1621 views
    This topic created in 1568 days ago, the information mentioned may be changed or developed.
    // 声明父类 function SuperClass() { this.superValue = true; } // 给父类添加公有方法 SuperClass.prototype.getSuperValue = function() { return this.superValue; } // 声明子类 function SubClass() { // 关键 SuperClass.bind(this); this.subValue = false; }; function inheritObject(o) { // 声明过渡函数对象(可以理解为类似子类) function F() {} // 过渡函数对象的原型 赋值为 父对象(理解为类似父类) F.prototype = o; // 返回过渡函数对象的实例,实例继承了父对象(父类) return new F(); } // subClass 传子类; superClass 传父类 function inheritPrototype(subClass, superClass) { // 复制父类的原型,保存在变量 let p = inheritObject(superClass.prototype); // 修复因为重写子类,导致子类的 constructor 属性被修改 p.cOnstructor= subClass; // 子类继承 subClass.prototype = p; } // 子类继承父类(关键) inheritPrototype(SubClass, SuperClass); // 给子类添加公有方法 SubClass.prototype.getSubValue = function() { return this.subValue; }; // 测试 let sub = new SubClass(); console.log(sub); console.log(sub.getSuperValue()); console.log(sub.getSubValue()); // instanceof 是判断前面的对象,是否是后面对象(类)的实例。不是判断是否是父类 console.log(sub instanceof SuperClass); // true console.log(sub instanceof SubClass); // true // 打印 

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    疑问:console.log(sub.getSuperValue());这输出预想是 true ,原型上也有 getSuperValue ,但 name 是""。

    是哪里代码写错了吗?

    求教哈大神们!

    5 replies    2022-01-12 10:13:13 +08:00
    cF06myaQ57WHKMBv
        1
    cF06myaQ57WHKMBv  
       Jan 10, 2022
    // 声明子类
    function SubClass() {
    // 关键
    #SuperClass.bind(this); //这里错了吧 应该是 call 或者 apply
    SuperClass.call(this);
    this.subValue = false;
    };
    zhaol
        2
    zhaol  
      &nbs;Jan 10, 2022
    SuperClass.bind(this)();
    zhaol
        3
    zhaol  
       Jan 10, 2022
    @zhaol bind 是返回一个改变了 this 的函数但是不会立即执行,call 和 apply 会立即执行
    gaocc
        4
    gaocc  
    OP
       Jan 12, 2022
    gaocc
        5
    gaocc  
    OP
       Jan 12, 2022
    嗯 感谢,是的。一下没注意
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