关于__proto__的链式记忆

实例化解析：functionFoo(){};varfoonewFoo();foo.__proto__Foo.prototype;foo.__proto__.__proto__

实例化解析：

function Foo() {};var foo = new Foo();foo.__proto__ === Foo.prototype;foo.__proto__.__proto__ === Object.prototype;foo.__proto__.__proto__.__proto__ === null;foo.prototype === undefined;foo.toString === Object.prototype.toString;

原形继承后的实例化解析：

function Bar() {};Bar.prototype.__proto__ = Foo.prototype;var bar = new Bar();bar.__proto__ === Bar.prototype;bar.__proto__.__proto__ === Foo.prototype;bar.__proto__.__proto__.__proto__ === Object.prototype;bar.__proto__.__proto__.__proto__.__proto__ === null;bar.prototype === undefined;bar.toString === Object.prototype.toString

对象bar，访问toString，整个链式过程如下：

bar.toString || bar.__proto__.toString || bar.__proto__.__proto__.toString || bar.__proto__.__proto__.__proto__.toString bar.toString === Object.prototype.toString

最终调用的是 Object.prototype.toString

奇怪的Foo.toString

Foo.__proto__ === Function.prototype;Foo.__proto__.__proto__ === Object.prototype;Foo.prototype.__proto__ === Object.prototype;// 神奇竟然不等于 Object.prototype.toStringFoo.toString === Object.toString;Foo.prototype.toString === Object.prototype.toString;

每个function生成的时候都直接被设置了toString 等于 Object.toString了。

参考文档

• 實體關係的確定
• A re-introduction to Javascript

有爱

希望本文对你有用 ^_^