javascript - 无法更改对象属性值

Question

我是 Javascript 的新手，我试过这个:

object1 = {};
object2 = Object.create(object1, {a:{value:1}});
object2.a = 2;

然后如果我显示 object2.a，它仍然是 1 而不是 2。这是为什么？

谢谢。

Answer 1

因为 Object.create() 不是你想的那样。

看这个ECMAScript 5: Object creation and property definition

There are three additional aspects of a property we can control, each given a boolean value:

1. writable: Controls whether or not the property can be assigned. If false, attempts at assignment will fail. Only applies to data descriptors.
2. enumerable: Controls whether or not this property will appear in for...in loops.
3. configurable: Controls whether or not the property can be deleted, and whether its property descriptor (other than writable) can be changed.

Each of these defaults to false if not supplied.

所以你需要的是:

var object1 = {};
var object2 = Object.create(object1, {
    a: {
        value: 1,
        writable: true
    },
});
object2.a = 2;

玩得开心:)