How to use JSON to create object that Inherits from Object Type?

Question

I know how to use JSON to create objects, but there doesn\'t seem to be away to use JSON to create an object that is of a specific object type.

Here\'s an example of an

Answer 1

You could allow new Person() to accept an object to populate attributes with as a parameter.

var you = new Person({ firstName: 'Mike' });

Answer 2

I don't imagine so. I'd create a function on the Person class to initialise from a JSON object if I were you.

function Person() {
    this.loadFromJSON = function(json) {
        this.FirstName = json.FirstName;
    };
}

If you didn't know what class the JSON object was representing beforehand, perhaps add an extra variable into your JSON.

{ _className : "Person", FirstName : "Mike" }

And then have a 'builder' function which interprets it.

function buildFromJSON(json) {
    var myObj = new json["_className"]();
    myObj.loadFromJSON(json);
    return myObj;
}

---

Update: since you say the class is part of a third-party library which you can't change, you could either extend the class with prototyping, or write a function which just populates the class externally.

eg:

Person.prototype.loadFromJSON = function(json) {
    // as above...
};

or

function populateObject(obj, json) {
    for (var i in json) {
        // you might want to put in a check here to test
        // that obj actually has an attribute named i
        obj[i] = json[i];
    }
}

Answer 3

You can derive an object from theirs. Your constructor can accept the object you want, but call their constructor in an unaffected fashion:

function yourWrapper(obj) {
    theirObject.call(this);
    for (var s in obj) {
        this[s] = obj[s];
    }
}
yourWrapper.prototype = new theirObject();

Or something like that :)