再说javascript 的__proto__ 和prototype 属性

Posted 2020-09-03 牛顿的小脑

过了一段时间，没写 原生的 javascript 的了，感觉天天在用框架写代码，框架写代码完全限定死了你所需要思考的东西，只是在处理一些业务逻辑，真正的代码

都感觉不会写了。 突然发现，框架用的不熟悉，原生的代码也忘得差不多了。感觉很难受，人生不能这样子度过！

　　重新翻开《javascript 高级程序设计》， 回归到本原。工作上用框架写代码没错，业余时间的话就要自己多写一点原生的代码，或者说研究、模仿、直到自己设计一个

框架出来。

js 中的类， 对象， 类的静态变量，类的继承 。
function Scope(){
} 

这样就是定义了一个类了。

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This figure again shows that every object has a prototype. Constructor function Foo also has its own __proto__ which is Function.prototype, and which in turn also references via its __proto__property again to the Object.prototype. Thus, repeat, Foo.prototype is just an explicit property of Foo which refers to the prototype of b and c objects.

var b = new Foo(20);
var c = new Foo(30);

What are the differences between __proto__ and prototype properties?

 

up vote23down vote

Prototype VS. __proto__ VS. [[Prototype]] When creating a function, a property object called prototype is being created automatically (you didn\'t create it yourself) and is being attached to the function object (the constructor). Note: This new prototype object also points to, or has an internal-private link to, the native JavaScript Object. Example: function Foo () { this.name = \'John Doe\'; } // Foo has an object property called prototype. // prototype was created automatically when we declared the function Foo. Foo.hasOwnProperty(\'prototype\'); // true // Now, we can assign properties to to the prototype object without declaring it first. Foo.prototype.myName = function () { return \'My name is \' + this.name; } If you will create a new object out of Foo using the new keyword, you basically creating (among other things) a new object that has an internal or private link to the function\'s prototype Foo we discussed earlier: var b = new Foo(); b.[[Prototype]] === Foo.prototype // true   The private linkage to that function\'s object called [[Prototype]]. Many browsers are providing us with a public linkage instead that called __proto__!   To be more specific, __proto__ is actually a getter function that belong to the native JavaScript Object and returns the internal-private prototype linkage of whatever the this binding is (returns the [[Prototype]] of b): b.__proto__ === Foo.prototype // true It is worth noting that starting of ECMAScript5, you can also use the getPrototypeOf method to get the internal private linkage: Object.getPrototypeOf(b) === b.__proto__ // true   NOTE: this answer doesn\'t intend to cover the whole process of creating new objects or new constructors, but to help better understand what is __proto__, prototype and [[Prototype]] and how it works.