为什么JavaScript中的静态私有变量是静态的？(Why are static private variables in JavaScript static?)

为什么JavaScript中的静态私有变量是静态的？(Why are static private variables in JavaScript static?)

我正在阅读Nicholas C. Zakas的Web开发人员第三版JavaScript（旧的，我知道），我很难理解为什么静态私有变量/函数首先是静态的。 我理解如果我声明一个带有私有变量/函数的构造函数，它的所有实例都有自己的私有变量/函数，就像在Zakas的一个例子中一样：

function MyObject(){ //private variables and functions var privateVariable = 10; function privateFunction(){ return false; } //privileged methods this.publicMethod = function (){ privateVariable++; return privateFunction(); }; }

那么如何将私有变量/函数放在私有作用域中会使变量变为静态？ 是因为它们被封闭在一个私人范围内，还是有一些我忽略的东西？ 这是Zakas关于静态私有变量的一个例子：

(function(){ //private variables and functions var privateVariable = 10; function privateFunction(){ return false; } //constructor MyObject = function(){ }; //public and privileged methods MyObject.prototype.publicMethod = function(){ privateVariable++; return privateFunction(); }; })();

I am reading Nicholas C. Zakas's JavaScript for Web Developers Third Edition (old, I know), and I am having trouble understanding why static private variables/functions are static in the first place. I understand that if I declared a constructor with private variables/functions, all of its instances would have their own private variables/functions, like in one of Zakas's examples:

function MyObject(){ //private variables and functions var privateVariable = 10; function privateFunction(){ return false; } //privileged methods this.publicMethod = function (){ privateVariable++; return privateFunction(); }; }

So how would putting private variables/functions in private scopes make the variables static? Is it just because they're enclosed in a private scope, or is there something I'm overlooking? Here's one of Zakas's examples on static private variables:

(function(){ //private variables and functions var privateVariable = 10; function privateFunction(){ return false; } //constructor MyObject = function(){ }; //public and privileged methods MyObject.prototype.publicMethod = function(){ privateVariable++; return privateFunction(); }; })();

最满意答案

在第一个示例中，每次调用MyObject privateVariable创建一个新的局部变量privateVariable 。

在第二个示例中， privateVariable是function(){ ... } ，只调用一次，因此只创建一个变量。 这个变量由MyObject.prototype.publicMethod ，然后由MyObject创建的所有对象共享。

In your first example, every time you call MyObject a new local variable privateVariable is created.

In your second example, privateVariable is part of function(){ ... }, which is only called once, so only one variable is ever created. This one variable is used by MyObject.prototype.publicMethod, which is then shared by all objects created through MyObject.