将Object.defineProperties与符号一起使用是否有效? [英] Is it valid to use Object.defineProperties with symbols?

问题描述

让我们采用以下代码:

var obj = {};
var x = Symbol();
Object.defineProperties(obj, {
  [x]: {
    value: true,
    writable: true
  },
  "property2": {
    value: "Hello",
    writable: false
  }
  // etc. etc.
});
console.log(obj[x])

这有效吗?

使用本地Object.defineproperties代码，我们在console.log中获得了true.

With the native Object.defineproperties code we get in the console.log true.

使用zone.js的polyfill

With the polyfill of zone.js

其形式为:

  Object.defineProperties = function (obj, props) {
    Object.keys(props).forEach(function (prop) {
      Object.defineProperty(obj, prop, props[prop]);
    });
    return obj;
  };

对于未定义的console.log，我们得到相同的代码.

we get for the same code of console.log undefined.

这是因为存在Object.keys函数.我四处搜寻，在任何地方都找不到是否应该允许这样做.

This is because of the Object.keys function. I googled around and did not find in any place if this should be allowed or not.

推荐答案

我四处搜寻，没有发现是否应允许这样做.

I googled around and did not find in any place if this should be allowed or not.

您始终可以检查规格，在这种情况下，§ 19.1.2.3 Object.defineProperties(O，Properties).

You can always check the spec, in this case § 19.1.2.3 Object.defineProperties(O, Properties).

它使用 OwnPropertyKeys内部方法，该方法的确列出了对象的所有字符串和符号键.

It uses the OwnPropertyKeys internal method, which does indeed list all string and symbol keys of an object.

这是由于Object.keys功能

正确.它应该是Object.getOwnPropertyNames(props).concat(Object.getOwnPropertySymbols(props)).您可能要使用zone.js提交错误.但是，我确实想知道为什么在使用ES6符号时为什么需要对ES5 Object.defineProperties函数使用polyfill?

Correct. It should be Object.getOwnPropertyNames(props).concat(Object.getOwnPropertySymbols(props)) instead. You may want to file a bug with zone.js. I do however wonder why you'd need a polyfill for the ES5 Object.defineProperties function when you're working with ES6 symbols?

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