使现有的不可写和不可配置的属性可写和可配置

问题描述

说我有一个对象:

var agent = new Agent({name: 'James', type: 'secret', id: 007})

构建Agent类时，我决定使id属性不可变:

When I built the Agent class, I decided to make the id property immutable:

Object.defineProperty(Agent.prototype, 'id', {
    configurable: false,
    writable: false
})

但是在某些时候，我想将对象标记为删除.而且由于我们实际上无法删除 this ，因此我将通过删除 id 属性来削弱对象.因此，我再次使该属性可写:

But at some point I will want to mark the object for deletion. And because we can't actually delete this, I'm going to cripple the object by removing the id property instead. So I go to make the property writable again:

Object.defineProperty(agent, 'id', {
    configurable: true,
    writable: true
})
delete agent.id

但是我当然知道:

TypeError: Cannot redefine property: id

因为 id 已经存在.

如何使现有不可写属性可写?

How can I make an existing non-writable property writable?

推荐答案

Mozilla文档说

换句话说，如果要稍后修改属性定义(以使其可写)，则必须在第一个属性定义中将 configurable 设置为 true .

In other words, you must set configurable to true in the first property definition if you want to modify the property definition (to be writable) later.

请注意，当 configurable 为 false 时，您可以采用另一种方法(将可写属性设置为不可写)，但这与您在此处所做的相反

Note that you can go the other way (make writable property non-writable) when configurable is false, but that is the opposite of what you're doing here.

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