toJSON method for nested Backbonejs objects

gistfile1.js

 var YourModel = Backbone.Model.extend({
	toJSON: function(){
		var obj = {};
		_( this.attributes ).each( function( val, key ){
			obj[ key ] = val && typeof val === "object" && "toJSON" in val ? val.toJSON() : val; 
		});
		return obj;
	}
 });