我可以安全地扩展javascript内置类吗？

Can I safely extend Javascript builtin classes, like Array?

我可以安全地扩展Javascript内置类,比如Array吗?

I.e. on which browsers/environments will the following not work:

即以下哪些浏览器/环境不起作用:

Array.prototype.double = function() { return  this.concat(this); }Array.twice = function(a) { return a.double(); }Array.twice([1, 2, 3]) # => [1, 2, 3, 1, 2, 3]

2 个解决方案

#1

Depends on your definition of "work".

取决于您对“工作”的定义。

There are three main issues with prototype extension.

原型扩展有三个主要问题。

it's global scope so there is name collision

它是全局范围,因此存在名称冲突

If your adding enumerable properties it breaks for .. in

如果您添加可枚举的属性,它会中断... in

Code is confusing to read, is this an ES5 feature or a custom library?

代码令人困惑,这是一个ES5功能还是自定义库?

It will work as in, Array.prototype and Array are mutable so you can add the code and call the properties.

它将起作用,Array.prototype和Array是可变的,因此您可以添加代码并调用属性。

However:

Array.prototype.trolls = 42;for (var k in []) {  alert(k === "trolls");}

The above is an example of it breaking for .. in. This is easily solved with

以上是打破...的例子。这很容易解决

Object.defineProperty(Array.prototype, "trolls", {  value: ...,  enumerable: false});

(ES5 only. Breaks in IE<9. can't be emulated in legacy engines)

(仅限ES5。IE <9中断。无法在旧版引擎中模拟)

or with

for (var k in []) {  if ([].hasOwnProperty(k)) {    alert(k === "trolls");  }}

Personally I avoid automatically extending natives for these exact reasons. However I think it's perfectly acceptable to have a .extendNatives function in your library like pd.extendNatives

我个人避免出于这些原因自动扩展原生代。但是我认为在你的库中有一个.extendNatives函数是完全可以接受的,比如pd.extendNatives

#2

Safely, not really - because you can't be sure you're the only one extending them, or that you're actually extending the correct methods (see Prototype - last time I checked, it was extending the builtin classes, which wreaked havoc on others scripts' expectations of the builtins' behavior). Modifying objects you don't own is a path to very tricky territory ("oh, but is this the actual built-in concat(), or did some other script change it behind our back?").

安全,不是真的 - 因为你无法确定你是唯一一个扩展它们的人,或者你实际上正在扩展正确的方法(参见Prototype - 我上次检查时,它正在扩展内置类,这会造成严重破坏关于其他脚本对内置行为的期望。修改你不拥有的对象是一条非常棘手的领域的路径(“哦,但这是实际的内置concat(),还是其他一些脚本在我们背后改变它?”)。

See e.g. this for a more detailed discussion: http://perfectionkills.com/extending-built-in-native-objects-evil-or-not/

参见例如这是一个更详细的讨论:http://perfectionkills.com/extending-built-in-native-objects-evil-or-not/

#1