json_prototype v1.0.1
jsonPrototypeJS
Use JSON.stringify(), .parse() and retain selected JS prototypes of your objects.
This is achieved by either providing special replacer/reviver functions to JSON.stringify() and JSON.parse() or by packing the object before the JSON serialization and unpacking the result after deserialization.
While inspired by resurrectJS, this approach is fully compatible with JSON.serialize() and JSON.parse() and thus does not impose a proprietary JSON (de)serializer. It however uses some of resurrectJS' ideas.
Furthermore, you may even use jsonPrototypeJS to prepare your objects before sending them via API functions which internally use whatever JSON (de)serializer. This is especially useful in Firefox Addons and that is where the need for this little tool arised.
Note: As in resurrectJS, the special number values Infinity, -Infinity and NaN are handled, too.
Synopsis
We assume 'myobject = new MyObject'. 'myobject' may contain some properties of 'class' MySubClass somewhere in the object tree.
Direct Serialization
json = JSON.stringify(myobject, jsonPrototype.pack); Direct Deserialization
constructorsHash = { MyObject: MyObject, MySubClass: MySubClass };
myobject = JSON.parse(json, jsonPrototype.unpack.bind(constructorsHash));Indirect Serialization
jsonPrototype.packObject(myobject);
json = JSON.stringify(myobject) /*could be any other JSON serializer*/;Indirect Deserialization
constructorsHash = { MyObject: MyObject, MySubClass: MySubClass };
myobject = JSON.parse(json) /*could be any other JSON deserializer*/;
jsonPrototype.unpackObject(myobject, constructorsHash);Prepare Your Code
Simply add a property named __PROTO__ to the prototype of every object you have to (de)serialize.
MyClass.prototype.__PROTO__ = 'MyClass';Your objects may contain arbitrary objects or arrays with or without the __PROTO__ property. jsonPrototypeJS will not look into objects which have a prototype other than Object.prototype. We might otherwise recurse into the DOM or into other 3rd party structures. Recursion happens only for plain objects, plain arrays or objects with prototype.__PROTO__.
If you'll (de)serialize Date and RegExp objects, you'll also have to add the __PROTO__ property to their prototype(s).
Date.prototype.__PROTO__ = 'Date';
RegExp.prototype.__PROTO__ = 'RegExp';Finally, you'll have to provide the constructors in a hash object indexed by name on the deserialization side and pass this to the unpack function(s):
constructorsHash = { MyObject: MyObject, MySubClass: MySubClass };
// Direct deserialization
myobject = JSON.parse(json, jsonPrototype.unpack.bind(constructorsHash));
// Indirect deserialization
myobject = JSON.parse(json);
jsonPrototype.unpackObject(myobject, constructorsHash);Note 1: Direct Deserialization cannot modify the outermost object, because the reviver function is not called for it. Either wrap your object into a plain object or use Indirect Deserialization!
Note 2: Direct Serialization cannot handle Date objects, because the reviver function gets called with the Date yet converted to a string using Date.toJSON(). You'll have to use Indirect Serialization!
Note 3: The property RegExp.lastIndex will get lost!
How it works
Each object with a prototype to retain receives a '#' property containing the constructor name (as in resurrectJS). During deserialization, the received plain object will be replaced by an object with the appropriate prototype which will be created using Object.create(constructorsHashvalueof#_property). This empty object with the now correct prototype is than populated with the properties from the received object. This is done using Object.assign().
Note: On browsers which do not have Object.assign() (i.e. IE), a polyfill is provided.
The original values of special number values, Date objects and RegExp objects (which are normally ignored by JSON.stringify()/.parse()) are transferred and recreated using special objects carrying their properties.
Platforms
- Major current Browsers
- node.js V0.4ff
- Rhino (tested with 1.7.6)
- IE 10ff
- IE9 may work, but I have none at hand
- IE8 does not work (misses Object.create() and related static functions)
Note: The code withstands the 'advanced' compression of the Google Closure compiler.
Sources
- GitHub (https://github.com/peter-ahr/jsonPrototypeJS)
- NPM: 'npm install json_prototype' (https://www.npmjs.com/package/json_prototype)
- bower: 'bower install json_prototype'