Javascript 如何在自定义 toJSON 方法中使用 JSON.stringify？
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How do you use JSON.stringify in a custom toJSON method?
提问by machineghost
So, JSON.stringify provides a great way to turn a JS object like:
因此，JSON.stringify 提供了一种很好的方法来转换 JS 对象，例如：
var baz = {"foo":1, "bar":someFunction};
in to a JSON string like:
到一个 JSON 字符串，如：
{"foo":1}
It does this with an optional second argument that controls which fields should be serialized:
它使用一个可选的第二个参数来控制哪些字段应该被序列化：
JSON.stringify(baz, ["foo"]);
That's great, but there's a problem. Let's say your "baz" is actually the property of another object, and you want to serialize that other object:
这很好，但有一个问题。假设您的“baz”实际上是另一个对象的属性，并且您想序列化该另一个对象：
someObject.baz = {"foo":1, "bar":someFunction};
JSON.stringify(someObject, ["baz"]);
Well, normally you would just define a toJSON method on baz, eg.:
好吧，通常你只需要在 baz 上定义一个 toJSON 方法，例如：
someObject.baz = {"foo":1, "bar":someFunction};
someObject.baz.toJSON = function() { /* logic to "toJSON" baz*/ }
JSON.stringify(someObject, ["baz"]);
Now, as I mentioned earlier, we have the perfect logic to "toJSON" baz already:
现在，正如我之前提到的，我们已经有了“toJSON” baz 的完美逻辑：
someObject.baz.toJSON = function() {
return JSON.stringify(baz, ["foo"]);
}
but if you try putting that in to your toJSON, you'll get a recursion error, because stringify will trigger the toJSON, which will trigger the stringify, which will ... :-(
但是如果你尝试把它放到你的 toJSON 中，你会得到一个递归错误，因为 stringify 将触发 toJSON，这将触发 stringify，这将...... :-(
You can work around this with a hack:
您可以通过 hack 解决此问题：
someObject.baz.toJSON = function() {
var oldToJON = this.toJSON;
this.toJSON = null;
var ret = JSON.stringify(baz, ["foo"]);
this.toJSON = oldToJON;
return ret;
}
But ... that just seems wrong. So, my question is: is there any way you can utilize the nifty built-in serialization power of JSON.stringify insidea toJSON method of an object (without having to hide the toJSON method itself during the stringify operation)?
但是……这似乎是错误的。所以，我的问题是：是否有可以利用漂亮的内置JSON.stringify序列化的功率任何方式内部对象的方法的toJSON（不必隐藏在字符串化操作过程中的toJSON方法本身）？
回答by casablanca
Crockford's json2.jssays:
A toJSON method does not serialize: it returns the value represented by the name/value pair that should be serialized, or undefined if nothing should be serialized.
toJSON 方法不会序列化：它返回由应该序列化的名称/值对表示的值，如果没有应该序列化，则返回 undefined。
So you are simply expected to return the value that you want serialized. In your case, baz.toJSONshould simply return the portion of the bazobject that you want serialized:
所以你只需要返回你想要序列化的值。在您的情况下，baz.toJSON应该简单地返回baz您想要序列化的对象部分：
someObject.baz.toJSON = function() {
return { foo: this.foo };
};
