Object-oriented programming and functional programming imply each other. While encoding closures as objects is a well-known technique (see the command pattern, and e.g. Functors in C++), using closures to implement objects is a bit more unusual.

In this post, I will explore creating a simple object system in JavaScript, using only the functional parts.

Many languages make a distinction between objects and classes. But shouldn't everything – including classes – be an object in a pure object-oriented language? Some languages like Smalltalk, Common Lisp, and Ruby manage just that and offer a complete and flexible Metaobject-Protocol. Others such as Java only offer a read-only object protocol commonly called “introspection” or “reflection”.

In this post, I'll explore how to create a simple Metaobject-Protocol where classes are objects – all without creating infinite loops. We'll be using a previous post's JavaScript object encoding as a basis for this MOP.