Fun(ctional) Javascript

@kirel

Why Javascript?*

*actually I'll use Coffeescript

• reach — Javascript runs everywhere
• Javascript has Good Parts
• Javascript has everything we need — except tail call optimization

functional programming

• first class functions
• higher order functions
• purity
• immutability (not today)
• composition
• partial application & currying
• recursion (neither)

purity

• data in, data out
• no sideeffects
• referential transparency

Example 1

Example 2

first class functions

Functions should be treated like everyone else...

Example

higher order programming

Functions taking functions as arguments and returning functions.

Example

partial application

Preloading / preconfiguring functions with arguments

Example

currying

[...] transforming a function that takes multiple arguments in such a way that it can be called as a chain of functions, each with a single argument (partial application)

— Wikipedia

Example

Interlude:

closures

How is this all working?

Example

intermezzo

Code

composition

Stitching functions together...

Example

underscore.js

Underscore is a utility-belt library for JavaScript that provides a lot of the functional programming support that you would expect in Prototype.js (or Ruby), but without extending any of the built-in JavaScript objects. It's the tie to go along with jQuery's tux, and Backbone.js's suspenders.

docs

scoreunder.js

Underscore got things backwards...

Code

Category Theory:

Functors & Monads

Just kidding...

source

What's my point?

point free

• programming without explicit arguments
• function decorators
• function combinators
• function composition
• currying

Code

finale

Another interactive example.

Und alle so: Yeah!

Code

Down the rabbit hole...

Books

• Functional Javascript by @fogus
• Javascript Allongé by @raganwald

Down the rabbit hole...

Links

• http://www.github.com/fogus/lemonad
• http://allong.es
• http://underscorejs.org but you should use
• http://lodash.com instead
• http://documentcloud.github.io/underscore-contrib/
• http://fitzgen.github.io/wu.js/
• http://osteele.com/sources/javascript/functional/
• http://coffeescript.org
• http://livescript.net
• https://github.com/clojure/clojurescript
• http://fay-lang.org

Down the rabbit hole...

Talks

by @drboolean

• http://www.youtube.com/watch?v=HAcN3JyQoyY#t=299
• http://www.youtube.com/watch?v=m3svKOdZijA
• http://www.youtube.com/watch?v=ww2Z1URx-G0