理解javascript全局命名空间和闭包

I'm trying to improve my understanding of the global namespace in javascript and I'm curious about a few things:

我正在努力提高我对javascript中全局命名空间的理解,我对以下几点感到好奇:

is there a "GOD" (i.e. a parent) object that all objects (since all things except primitives are objects) to answer to and if so would that object be "window" ?
有一个“GOD”(即父级)对象,所有对象(因为除了基元之外的所有东西都是对象)要回答,如果是,那么该对象是“窗口”吗?
why is it bad idea to have vars/functions on a global level?
为什么在全球范围内拥有变量/功能是个坏主意?

if it is really a bad idea to have vars/functions in global scope then would closures be the best way to avoid this? example:

如果在全局范围内拥有vars /函数真的是一个坏主意那么闭包是避免这种情况的最佳方法吗?例:

function parent(){
    var x = 'some value';//this var would be considered global to all children functions but not in the true global namespace
    function child1(){
        x.someMethod()
    } 
    function child2(){
        x*something;
    }
    function child3(){
        x+=something;
        child2()
        child1()
    }
    child3()
}
parent()

4 个解决方案

#1

Is there a god (i.e. a parent) object?

有神(即父母)对象吗?

Yes. More technically, it's the global object that all these primitives are members of; it just happens that in the browser, the window object is the global object.
是。从技术上讲,它是所有这些原语都是其成员的全球对象;它恰好发生在浏览器中,窗口对象是全局对象。
```
> window.String === String;
true
```
Why is it bad idea to have vars/functions on a global level?

为什么在全球范围内拥有变量/功能是不错的主意?

Because if you're adding lots of 3rd party libraries/ scripts, they all share the same global object, there's the chance of name collisions. This is a real life problem with all the libraries which use $ as an alias (jQuery, Prototype and more).
因为如果你要添加许多第三方库/脚本,它们都共享同一个全局对象,那么就有可能发生名称冲突。这是使用$作为别名(jQuery,Prototype等)的所有库的真实问题。
If it is really a bad idea to have vars/functions in global scope then would closures be the best way to avoid this?

如果在全局范围内拥有vars /函数真的是一个坏主意那么闭包是避免这种情况的最佳方法吗?

x shouldn't be considered global. It's part of the closure formed by declaring the child functions inside the parent() function. The problem part of your snippet is that parent() is global; what happens if some other code re-declared parent()? This would be better:
x不应被视为全球性的。它是通过在parent()函数中声明子函数而形成的闭包的一部分。你的代码片段的问题部分是parent()是全局的;如果其他一些代码重新声明parent()会发生什么?这会更好:
```
(function () {

function parent(){
    var x = 'some value';
    function child1(){
        x.someMethod()
    } 
    function child2(){
        x*something;
    }
    function child3(){
        x+=something;
        child2()
        child1()
    }
    child3()
}
parent()

}());
```
The fact x is accessible within the child functions isn't bad; you should have written those functions yourself, so you should be aware of the existence of x. Bear in mind that if you re-declare x within those child functions with var, you won't affect the x in parent().
在子函数中可以访问x的事实并不错;你应该自己编写这些函数,所以你应该知道x的存在。请记住,如果使用var在这些子函数中重新声明x,则不会影响parent()中的x。

4 个解决方案

#1

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