Dynamically creating a new javascript class from an existing object

Question

Say I have the following code:

var album = new MyObject('album');

Assume that when the object is constructed, a bunch of properties relative to only albums are loaded via AJAX. Would it be possible to create an Album class so that at a later point, I may just do this:

var anotherAlbum = new Album();

The Album constructor would automatically set the properties that are unique to album objects, based on what was loaded when creating MyObject('album')

Answer 1

JavaScript "classes", just like any other object, can be dynamically created. So, yes, this can be done.

You would do something like this in the code handling the AJAX response (assuming that the AJAX response was providing the name of the new "class", and it's in a variable called newClassName):

window[newClassName] = function() {
  // New class name constructor code
}

window[newClassName].prototype = {

  someProperty: "someValue",

  someMethod: function(a, b) {
  },

  someOtherMethod: function(x) {
  }
}

Answer 2

This is actually the only for of inheritance that JavaScript has. JavaScript has prototypal inheritance (which can be used to recreate classical inheritance). That means that inheritance is from another object, not a class definition.

To create an object that has all the properties of another object is simple:

function Album() {
   // do whatever initialization you need to here, all the properties of album 
   // are available on 'this'
   // e.g.,
   doSomething(this.albumName);
}
Album.prototype = album;

var anotherAlbum = new Album();