再说javascript 的proto 和prototype 属性

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.

时间： 2024-10-27 12:05:08

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