JavaScript如何“可写”属性描述符工作？ [英] How does JavaScript "writable" property descriptor work?

问题描述

为什么JavaScript可写属性描述符不禁止任何属性更改？

Why does the JavaScript "writable" property descriptor not forbid any property changes?

例如：

var TheDarkKnight = Object.create(Superhero, {
    "name": {
        value:"Batman",
        writable:"false"
    }
});

TheDarkKnight.name; //"Batman";

TheDarkKnight.name = "Superman";
TheDarkKnight.name; //"Superman";

我认为 TheDarkKnight.name 仍应返回蝙蝠侠我尝试将其更改为其他值后，因为我将可写属性描述符设置为 false 。

I thought TheDarkKnight.name should still return "Batman" after I tried to change it to another value because I set the "writable" property descriptor to false.

那么如何以正确的方式使用它？

So how to use it in the right way?

推荐答案

它应该是 false ，而不是false。换句话说，它应该是一个布尔值。

It should be false, not "false". In other words, it should be a boolean.

如果你没有传递一个布尔值，那么你提供的任何值都将被强制转换为布尔值，并且 Boolean（false）=== true; // true ，所以你实际上传递了 writable：true 。

If you don't pass a boolean, then whatever value you give will be coerced to a boolean, and Boolean("false") === true; // true, so you were effectively passing writable:true.

var TheDarkKnight = Object.create(Superhero, {
    "name": {
        value:"Batman",
        writable:false // boolean false (or any falsey value)
    }
});

TheDarkKnight.name; //"Batman";

TheDarkKnight.name = "Superman";
TheDarkKnight.name; //"Batman";

另外，请注意 writable：false 是默认值，因此如果您只是从描述符中删除该设置，该属性将不可写。

Also, note that writable:false is the default value, so if you just remove that setting from the descriptor, the property will not be writable.

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