How to add methods to a (JSON) object's prototype?

Question

Let\'s say I receive some JSON object from my server, e.g. some data for a Person object:

{firstName: \"Bjarne\", lastName: \"Fisk\"}

Now,

Answer 1

If you're dealing with plain JSON data then the prototype of each person object would simply be Object.prototype. In order to make it into an object with a prototype of Person.prototype you'd first of all need a Person constructor and prototype (assuming you're doing Javascript OOP in the traditional way):

function Person() {
    this.firstName = null;
    this.lastName = null;
}
Person.prototype.fullName = function() { return this.firstName + " " + this.lastName; }

Then you'd need a way to turn a plain object into a Person object, e.g. if you had a function called mixin which simply copied all properties from one object to another, you could do this:

//example JSON object
var jsonPerson = {firstName: "Bjarne", lastName: "Fisk"};

var person = new Person();
mixin(person, jsonPerson);

This is just one way of solving the problem but should hopefully give you some ideas.

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Update: Now that Object.assign() is available in modern browsers, you could use that instead of writing your own mixin function. There's also a shim to make Object.assign() work on older browsers; see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign#Polyfill.