What is Ferp

Summary of what ferp is, and why you would want to use it.

tl;dr

Simply put, Ferp is a Javascript library to functionally manage your application's state. The main attraction of Ferp is that side-effects and subscriptions take a front-row seat. Ferp also has no opinion on your end-interface, be it a command line application, server, desktop application, or front-end web application.

Project Goals

Every interaction outside of your application is a side effect

Does your app generate a random number, get the current timestamp, or handle user input? If so, you are relying on side-effects. Side-effects, or simply effects, aren't bad at all, but they can make testing and logic hard. Ferp's update loop puts the power of controlled effects into the hands of every developer.

Effects should be composable

In most cases, effects cause other effects. For example, to add a notification in the browser, you must first ask permission. These are two separate side effects that should be able to be composed, something like notifyPermit(notifySend('Holy notification, Batman!')). This pattern can prevent unnecessary update calls, and keeps side-effect producing code out of your state.

State has nothing to do with presentation

Much like many state management libraries that have come before, ferp has no preconceived notion of how you want to present your app. Use your favourite front-end or back-end library, or your custom one-of-a-kind solution. I would even argue that presentation is a form of a side-effect, since it often times modifies state outside of your applications control.

Is Ferp Right for Your Project?

Ferp solves a certain combination of problems, but it does not claim to be the most correct way to solve these problems. The following table compares some of the key features of ferp to other popular libraries.

Feature	Ferp	Redux	Mobx
State is...	immutable	immutable	mutable
Update mechanism	effects	actions	observables
Number of stores	single	single	multiple
Side-effect support	built-in	plugins	built-in
Subscription support	functions	redux-saga?	observables

Consider the problems your application is going to face, and evaluate all your options. This includes considering the libraries you may import, the existing code you have, and of course, the features you need.

Links

• Check out the code over at github.com/ferp-js/ferp
• Learn more about me at my website, mrbarry.com