JavaScript：为什么在所有者搜索代码中我得到的是假而不是真？

Question

I learn JavaScript and play with it. Why I get false instead of true in my code of property owner searching? What is my mistake?

/* Get the object containing the property. */
Object.prototype.where = function (propName){ return this.hasOwnProperty(propName) ? this :
    (this.constructor.prototype ? null : this.where.bind(this.constructor.prototype, propName)());};

let a = {foo : 123}, b = Object.create(a), c = a == b.where('foo');

process.stdout.write(c.toString()); // false

Answer 1

Because b.constructor.prototype != a . You will want to use Object.getPrototypeOf to follow the prototype chain.

Answer 2

a=Object.create(b);
//constructor: Object
//constructor.prototype: Object.prototype

//really inherits from: b

a = new b();
//constructor: b
//constructor.prototype: b.prototype

//really inherits from: b.prototype

Your code just works with constructor functions and the new operator, in all the other cases it goes wrong, as it does not inherit from the constructors prototype directly. It would be better to look up the prototype chain instead:

Object.where = function (obj,propName){ 
  return obj.hasOwnProperty(propName) ? 
   obj :
(!Object.getPrototypeOf(obj) ? null : Object.where(Object.getPrototypeOf(obj), propName));
};

Object.where(Object.create({a:0}),"a");

Note that overriding Object.prototype is a bad idea, as it confuses all for loops. So one may set enumerable to false, or one simply make it static...