Functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data. Some key aspects of functional programming include: breaking problems down into smaller pure functions, using functions as first-class citizens that can be passed in and returned from other functions, avoiding side effects from functions, and embracing concepts like referential transparency. JavaScript supports functional programming with features like first-class functions, higher-order functions, immutability, and functional utilities like map and reduce. Functional programming can make code more readable, reusable, and easier to understand when working with larger teams or on larger applications.

1. Functional Programming
With JavaScript

2. In the beginning, God created “Programming
paradigms” in 7 days (Genesis 101)👼
Imperative Programming
Procedure Programming
Object Oriented Programming
Functional Programming
~ a coding style / a way of thinking

3. တူတတောော်တ ောငော်တ ို့

4. တ ေးတေတောပဲ ဘောထူေးလ ို့လဲ
Q: Don’t we write functions in every language ?
A: But functional programming take it to a whole another level
Def : Break any complex problem down into smaller sub-problems, solve them
using functions, and finally combine them together to solve the bigger
problem.

5. ဘယော်သူတတွေသေးလ ို့လဲ
F#, C# (.NETs)
Lisp & Perl (grandpas)
Erlang , Elixir & Haskell (hotshots)
Clojure & Scala (JVMs)
D, R, JS, Python, … (sexies)

6. Why FP in JavaScript
The root of all evil is “this” keyword 😈
Object.prototype
OOP in JS is like sugar coated paracetamol 💊
.call .apply .bind // anyone ?

7. Input => process => output
f(x) = x * x // function (x) { return x * x }
g(f(x))
“ Programmer think of their programs more
as pipes for data to travel through just like
we did in Math “
Source ~ wellesley.edu

8. Imperative
let name = “azb”
let greeting = “Hello, I’m ”
console.log(greeting + name)
function greeting(name){
return “Hello, I’m ” + name
}
greeting(“azb”)
Functional

9. First-class citizen အခွေငော်ို့ထူေးခ လူတေော်ေးစောေး
Treat like other values
Pass around arguments and return as value
Define and manipulate functions from other functions
Reference from variable or self

10. Side Effects
Changing the value of a variable (parent/ global), OBVIOUSLY
Writing some data to disk, file, console, network
Manipulating of UI
Calling external process
Generally - STATE CHANGED

11. Pure functions (no side effects)

12. High-order function (return)

13. High-order function (accept)

14. Referential transparency
function add(a, b) { return a + b }
add(add(2, 3), add(4, 1))
add((2 + 3), add(4, 1))
add((2 + 3), (4 + 1))
(2 + 3) + (4 + 1)

15. Don’t LOOP (stream of data / HO funs)
.forEach
.map
.reduce
.filter

16. Immutability is bad
.pop .push
.shift .unshift
let a = 1
a = “hello world”

17. Persistent data structures
var, let, const right ? ahuh not really
Wait a min Object.freeze Object.seal
MORI
IMMUTABLE (sponsored by facebook)
Underscore
Lodash
Ramda

18. More FP
Currying
Tail Recursion
Pattern matching
Infinite data structure
Composition
Lazy evaluation
self.Q&A
Concurrency
Parallelism
Async

19. READABLE, EASY TO UNDERSTAND,
REUSABLE
Writing with a larger team
Application larger than a todo app
Performance are not critical
You have to support the project
P.S
1. I/O is tricky in FP
2. Code LineNums are just a number
3. There’s no single true paradigm

20. Aung Zan Baw - တအောငော်ဇတဘောော်
Web developer (Fairway Technology)

21. Links
Slides - https://goo.gl/3fmMXk
Best FP in JS - https://goo.gl/IqmkoT
ReactiveX !!!
Starter book - https://goo.gl/ctmBTo