ORM and JSON in JavaScript and TypeScript

Mapping JSON to entity objects and objects to JSON is trivial, if the objects only contain data and allow direct access to the properties. There is a bit more work if the class needs to have helper methods for things like validation, and if we want to wrap the data members with getters and setters.

The goal is to meet these requirements during coding:

• Entity classes may include validation
• Data members have accessor (getters and setters)
• Entity classes may have other methods
• Entity class type is important (this encapsulates the previous three points)
• Missing data in the JSON source should be logged.
• Extra data in the JSON source should be logged.
• Support DRY - Don't Repeat Yourself

Full disclosure here: I know that there are two big problems with what I am about to describe. If you have been trying to handle ORM conversion already, you may have hit them. The problems are not insurmountable, but we'll get to that later.