Fantasy Land
Sometimes, the truth is stranger than fiction.
Fantasy Land is a collection of functional base libraries and a formal specification for how to implement "algebraic structures" in JavaScript. More specifically, Fantasy Land specifies the interoperability of common algebraic structures, or algebras for short: monads, monoids, setoids, functors, chains, and more. Their names may sound scary, but they're just a set of values, a set of operators, and some laws it must obey. In other words, they're just objects.
Here's how it works. Each algebra is a separate Fantasy Land specification and may have dependencies on other algebras that need to be implemented.
Some of the algebra specifications are:
- Setoids:
- Implement the reflexivity, symmetry and transitivity laws
- Define the
equals()method
- Semigroups
- Implement the associativity law
- Define the
concat()method
- Monoid
- Implement right identity and left identity
- Define the
empty()method
- Functor
- Implement the identity and composition laws
- Define the
map()method
The list goes on and on.
We don't necessarily need to know exactly what each algebra is for but it certainly helps, especially if you're writing your own library that conforms to the specifications. It's not just abstract nonsense, it outlines a means of implementing a high-level abstraction called category theory. A full explanation of category theory can be found in , Category Theory.
Fantasy Land doesn't just tell us how to implement functional programming, it does provide a set of functional modules for JavaScript. However, many are incomplete and documentation is pretty sparse. But Fantasy Land isn't the only library out there to implement its open source specifications. Others have too, namely: Bilby.js.
