toJSON() 和 JSON.Stringify() 的区别 [英] Difference between toJSON() and JSON.Stringify()

问题描述

如果您需要读取或克隆模型的所有数据属性，请使用其toJSON() 方法.此方法返回属性的副本作为对象(尽管它的名字不是 JSON 字符串).(当 JSON.stringify() 是传递一个带有 toJSON() 方法的对象，它将返回字符串化toJSON() 的值而不是原始对象.中的例子上一节在调用时利用了此功能JSON.stringify() 记录模型实例.)

if you need to read or clone all of a model’s data attributes, use its toJSON() method. This method returns a copy of the attributes as an object (not a JSON string despite its name). (When JSON.stringify() is passed an object with a toJSON() method, it stringifies the return value of toJSON() instead of the original object. The examples in the previous section took advantage of this feature when they called JSON.stringify() to log model instances.)

http://addyosmani.github.io/backbone-fundamentals/#backbone-基础

谁能告诉我这两种用 JSON 表示法表示对象 的区别.我只是很困惑这些是否达到相同或不同.

Can anyone tell me the difference between both these ways of representing an object in JSON notation. I am just confused whether these to achieve the same or there is a difference.

推荐答案

来自 精美手册:

toJSON 行为

如果一个被字符串化的对象有一个名为 toJSON 的属性，它的值是一个函数，那么 toJSON 方法会自定义 JSON 字符串化行为:而不是对象被序列化，toJSON 方法在调用时返回的值将被序列化.

If an object being stringified has a property named toJSON whose value is a function, then the toJSON method customizes JSON stringification behavior: instead of the object being serialized, the value returned by the toJSON method when called will be serialized.

这就是 Backbone 使用 toJSON 方法进行序列化并给定一个名为 m，你可以这样说:

This is why Backbone uses the toJSON method for serialization and given a model instance called m, you can say things like:

var string = JSON.stringify(m);

并且只从 m 中获取属性而不是一堆你的服务器不会关心的噪音.

and get just the attributes out of m rather than a bunch of noise that your server won't care about.

也就是说，主要区别在于 toJSON 生成一个值(数字、布尔值、对象等)，该值被转换为 JSON 字符串，而 JSON.stringify 总是产生一个字符串.

That said, the main difference is that toJSON produces a value (a number, boolean, object, ...) that gets converted to a JSON string whereas JSON.stringify always produces a string.

默认 Backbone toJSON 很简单这(对于模型):

The default Backbone toJSON is simply this (for models):

return _.clone(this.attributes);

so m.toJSON() 为您提供模型属性的浅层 副本.如果有数组或对象作为属性值，那么您将结束意外的引用共享.请注意，Backbone.Model#clone 也遇到这个问题.

so m.toJSON() gives you a shallow copy of the model's attributes. If there are arrays or objects as attribute values then you will end unexpected reference sharing. Note that Backbone.Model#clone also suffers from this problem.

如果你想安全地克隆一个模型的数据，那么你可以通过 JSON.stringify 然后通过 JSON.parse 发送它以获得一个深层副本:

If you want to safely clone a model's data then you could send it through JSON.stringify and then JSON.parse to get a deep copy:

var data         = JSON.parse(JSON.stringify(model_instance));
var cloned_model = new M(data);

其中 model_instance 是您的 Backbone 模型 M 的实例.

where model_instance is your instance of the Backbone model M.

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