Why Object.prototype.
In JavaScript non-standard property __ proto__ and function Object.getPrototypeOf (...) return the internal property [[Prototype]].
For all functions the property 'prototype' is an instance of Object.prototype, for example:
Array.prototype instanceof Object//true
But not so with Object.prototype:
Object.prototype.__proto__ === null //true
Object.getPrototypeOf( Object.prototype ) === null //true
mozilla developer documentation only says:
An Object's proto property references the same object as its internal [[Prototype]] (often referred to as "the prototype"), which may be an object or, as in the default case of Object.prototype. proto , null .
Would it be more appropiate that Object.prototype. proto or failing Object.getPrototypeOf (Object.prototype) return Object.prototype?
Is this a bug? Is this ok? why?
The prototype chain has to stop somewhere.
Had Object.getPrototypeOf( Object.prototype ) === Object.prototype , the JS engine would get into an infinite loop when it tries to resolve something from the prototype.
It would walk up the prototype chain to Object.prototype , and, if it doesn't find it there, it would walk further up to Object.prototype again, ad infinitum.
In fact, if you try to do that yourself, you'll get an error:
> Object.prototype.__proto__ = Object.prototype
Error: Cyclic __proto__ value
Note that you can also create your own objects with no [[Prototype]] by calling Object.create(null) .
上一篇: .extend，而不是类的原型？