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Functional reactive programming for JavaScript and CoffeeScript.


A collection of useful JavaScript functions to support a functional style of programming that takes advantage of ES6 features like iterators, generators, and promises. Fairmont is inspired by Underscore, EssentialJS, and

Why Fairmont?

Fairmont offers a combination of features we couldn't find in existing libraries. In particular, we wanted:

  • To use a functional programming style, even when performing asynchronous operations…

  • While coming as close to inline code for performance as possible (read: use lazy evaluation when working with collections)…

  • Taking full-advantage of ES6 features like iterators, generators, and promises, which offer powerful new ways of doing things

For example, here's how we would define a function that takes a path and returns a content-addressable dictionary of the files it contains.

content_map = async (path) ->
  paths = collect map (compose resolve, join path), yield readdir path
  assoc zip (map (compose md5, read), paths), paths

We've seamlessly integrated asynchronous functions with synchronous functions, even when doing composition. Behind the scenes we're using iterators to avoid multiple passes across the data. We make two passes here, even though it appears that we're making five.

Fairmont is also a literate programming project—the documentation, code, examples, and tests are together, making it easy to see what a function does, how it does it, and why it does it that particular way.

Function Reference


Fairmont is still under heavy development and is alpha quality, meaning you should probably not use it in your production code.


You can get an idea of what we're planning by looking at the issues list. If you want something that isn't there, and you think it would be a good addition, please open a ticket.