Javascript: how to un-jsonify efficiently/correctly

Question

To be honest, I'm not quite sure where to start with this question. I'll describe the situation: I am in the process of making a level editor for an HTML5 game. The level editor is already functional - now I would like to save/load levels created with this editor.

Since this is all being done in Javascript (the level editor as well as the game), I was thinking of having the save simply convert the level to a JSON and the load, well... un-jsonify it.

The problem is - the level contains several types of objects (several different types of entities, several types of animation objects, etc...) Right now, every time I want to add an object to the game I have to write an unjsonify method specifically for that object and then modify the level object's unjsonify method so it can handle unjsonifying the newly defined type of object.

I can't simply use JSON.parse because that just returns an object with the same keys and values as the original had, but it is not actually an object of that class/prototype. My question is, then, is there a correct way to do this that does not require having to continuously modify the code every time I want to add a new type of object to the game?

Answer 1

I would create serialise/deserialise methods on each of your objects to put their state into JSON objects and recover it from them. Compound objects would recursively serialise/deserialise their children. To give an example:

function Player {
  this.weapon = new Weapon();
}

Player.prototype.serialise = function () {
  return {'type': 'Player', weapon: this.weapon.serialise()};
}

Player.deserialise = function(json_object) {
  var player = new Player();
  player.weapon = Weapon.deserialise(json.weapon);
  return player;
}

Obviously in real code you would have checks to make sure you were getting the types of objects that you expect. Arrays and simple hash objects could be simply copied during serialisation/deserialisation though their children will often need to be recursed over.