The document is a presentation about everyday functional programming in JavaScript. It discusses how functional programming uses functions as atomic units with known input/output behavior rather than objects. Immutable data is preferred to simplify parallel processing and declarative code is easier to read. The presenter will do a live coding demo covering concepts like unit testing, refactoring, function composition, currying, data immutability, and using high order functions instead of loops.

1. Everyday Functional
Programming in
JavaScript
Leo Hernandez
@leojh

2. About Me
● From South Florida
● Been developing since 2004
● Started out in .Net but now mostly JavaScript
● Really excited about JavaScript world and
newer ways of doing the same thing
@leojh

3. WHY?
@leojh

4. In Functional Programming
code is built by using
Functions as atomic units
@leojh

5. Functions are good atomic
units because they have a
known input -> output lifecycle
@leojh

6. Unlike Objects, they tend to be
simple and have no side
effects
@leojh

7. const square = x => x^2
@leojh

8. In Functional Programming,
data is supposed to be
immutable
@leojh

9. Data Immutability helps with
keeping things simple and with
parallel processing
@leojh

10. Part of the goal is to make the
code declarative so it’s easier
to read since it conveys
intention
@leojh

11. const myBestCustomers = customers =>
customersWhoBuyATonFromMe(customers)
.and
.giveMeGoodReviewsOnYelp(customers)
@leojh

12. You’re probably already
working in FP and may not
realize it
@leojh

13. If you’re using React, you’re
basically using a plain JS
Function to render things on a
screen
@leojh

14. const ArticleTitle = title =>
<h3>{title}</h3>
@leojh

15. Let’s do some live coding
@leojh

16. Concepts During Live Coding
● Unit Testing
● Refactoring
● Function Composition
● Curry
● Data Immutability and transformation /
projections
● ES6+
@leojh

17. COMPOSE
VS
PIPE
@leojh

18. Use Spread Operators
@leojh

19. Before you write any
traditional loop, ask yourself
why?
You should probably use a
High Order Function instead
@leojh

20. THANK YOU!
@leojh