我可以安全地扩展javascript内置类吗？ [英] Can I safely extend javascript builtin classes?

问题描述

我可以安全地扩展Javascript内置类，例如 Array ？

在其上的浏览器/环境将无法工作：

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

解决方案

取决于你对工作的定义。

原型扩展有三个主要问题。

• 如果你添加可枚举的属性，它在中打破


• 代码很容易阅读，这是ES5功能还是自定义库？

它将像在 Array.prototype 和 Array 中一样工作，因此您可以添加代码并调用属性。

但是：

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

上面是一个破坏的例子。 。in 。这很容易用

解决。

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

（仅限ES5。在旧版引擎中无法模拟IE

或与

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

个人我避免自动扩展本地人因为这些确切的原因。但我认为在你的库中有 .extendNatives 函数是完全可以接受的，例如 pd.extendNatives

Can I safely extend Javascript builtin classes, like Array?

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

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]

解决方案

Depends on your definition of "work".

There are three main issues with prototype extension.

• it's global scope so there is name collision
• If your adding enumerable properties it breaks for .. in
• Code is confusing to read, is this an ES5 feature or a custom library?

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

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

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

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

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

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