在JavaScript中定义只读属性 [英] Defining read-only properties in JavaScript

问题描述

给定一个对象 obj ，我想定义一个只读属性'prop'并设置它值为 val 。这是正确的方法吗？

Given an object obj, I would like to define a read-only property 'prop' and set its value to val. Is this the proper way to do that?

Object.defineProperty( obj, 'prop', {
    get: function () {
        return val;
    }
});

结果应该是（对于 val ='test'）：

obj.prop; // 'test'
obj.prop = 'changed';
obj.prop; // still 'test' since it's read-only

此方法适用于btw：http://jsfiddle.net/GHMjN/

我只是不确定这是否是最简单/最顺利/最合适的方式这样做...

This method works btw: http://jsfiddle.net/GHMjN/
I'm just unsure if this is the easiest / smoothest / most proper way to do it...

推荐答案

您可以使用可写属性属性描述符，它可以防止需要 get 访问者：

You could instead use the writable property of the property descriptor, which prevents the need for a get accessor:

var obj = {};
Object.defineProperty(obj, "prop", {
    value: "test",
    writable: false
});

如评论中所述，可写选项默认为 false 所以你可以在这种情况下省略它：

As mentioned in the comments, the writable option defaults to false so you can omit it in this case:

Object.defineProperty(obj, "prop", {
    value: "test"
});

这是ECMAScript 5所以不适用于旧浏览器。

This is ECMAScript 5 so won't work in older browsers.

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