实现 instanceOf #161

Activity

1. sisterAn

   added

   虾皮

   on Mar 18, 2021
2. xiaoerwen commented on Mar 19, 2021

   

   xiaoerwen

   on Mar 19, 2021

   Last edited by xiaoerwen

   More actions

   Object.prototype.fakeInstanceOf = function(constructor) {
       let obj = this;
       while (true) {
           if (obj.__proto__ === null) {
               return false;
           }
           if (obj.__proto__ === constructor.prototype) {
               return true;
           }
           obj = obj.__proto__;
       }
   }

   考察的是原型链的使用，判断一个对象是否是某个构造函数的实例，即看构造函数的原型是否在该对象的原型链上。
3. evatxu commented on Apr 6, 2021

   

   evatxu

   on Apr 6, 2021

   More actions

   function myInstanceof(instance, target) {
       const targetProto = target.prototype,
                 instanceProto = instance.__proto__;
       while(instanceProto) {
         if (instanceProto === targetProto) return true;
         instanceProto = instanceProto.__proto__;
      }
      return false;
   }