解决IE8破坏的Object.defineProperty实现问题

问题描述

使用ECMAScript5的 Object.defineProperty 功能考虑以下代码：

Consider the following code, using ECMAScript5's Object.defineProperty feature:

var sayHi = function(){ alert('hi'); };
var defineProperty = (typeof Object.defineProperty == 'function');
if (defineProperty) Object.defineProperty(Array.prototype,'sayHi',{value:sayHi});
else Array.prototype.sayHi = sayHi;
var a = [];
a.sayHi();

适用于Chrome和Firefox 4（其中 defineProperty exists），适用于Firefox 3.6（其中 defineProperty 不存在）。但是，IE8 。因此，它尝试运行 Object.defineProperty 方法，但随后失败（浏览器中未显示错误）并停止在页面上运行所有其他JavaScript代码。

This works for Chrome and Firefox 4 (where defineProperty exists), and it works for Firefox 3.6 (where defineProperty does not exist). IE8, however, only partially supports defineProperty. As a result, it attempts to run the Object.defineProperty method, but then fails (with no error shown in the browser) and ceases to run all other JavaScript code on the page.

有没有更好的方法来检测和避免IE8的实施中断：

Is there a better way to detect and avoid IE8's broken implementation than:

if (defineProperty){
  try{ Object.defineProperty(Array.prototype,'sayHi',{value:sayHi}); }catch(e){};
}
if (!Array.prototype.sayHi) Array.prototype.sayHi = sayHi;

对于好奇，我在库，用于在支持此功能的浏览器中定义不可枚举的数组方法，并回退旧版浏览器的可枚举方法。

For the curious, I'm using this in my ArraySetMath library to define non-enumerable array methods in those browsers that support this, with a fallback to enumerable methods for older browsers.

推荐答案

我认为没有比使用try / catch进行直接功能测试更好的方法。这实际上正是IE团队在最近的帖子中推荐的。

I don't think there's a better way than a direct feature test with try/catch. This is actually exactly what IE team itself recommends in this recent post on transitioning to ES5 API.

您可以将测试缩短为类似 Object.defineProperty（{}，'x'，{}）（而不是使用 Array.prototype ），但这是一个小狡辩;您的示例测试了确切的功能（因此误报的可能性更小）。

You can shorten the test to just something like Object.defineProperty({}, 'x', {}) (instead of using Array.prototype) but that's a minor quibble; your example tests exact functionality (and so has less chance of false positives).

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