Dave L.
Software Engineer and Aspiring Software Craftsman
FP with Ramda
Content
- FP: Practical Explanation
- Ramda: What is it about?
- Code Examples
Functional Programming
- (almost) everything is a function
- functions are (almost) always pure
- immutable state (== no object manipulation)
Difference to OOP:
o.f() vs. f(o)
Ramda
enables FP with JS
What is it?
- Utility Library (comparable to Lodash, Underscore)
- pure functions, immutable state
AND:
- Every function is curried by default
- data to operate on comes last
CurrYING
apply parameters of a function in several calls
Goal: have unary functions
// A normal function with two arguments
const myFunction = (param1, param2) => { console.log(`I got called with ${param1} ${param2}` };
myFunction('Hello', 'World') // I got called with Hello World// Now lets curry it
import {curry} from 'ramda';
const myCurriedFunction = curry(myFunction);
// does NOT execute the function, but stores the first arugment
const myCurriedHelloFunction = myCurriedFunction('Hello');
// ... do other things and then later
myCurriedHellFunction('World') // now prints 'I got called with Hello World');Operated data comes last
_.forEach([1,2,3], (val) => console.log(val));
ramda.forEach((val) => console.log(val), [1,2,3]);FUNCTION COMPOSITION
the big Goal
example time
Use case
The price for all selected products should be calculated and displayed as followed:
- take all price relevant products. Price relevant means: they are selected, are in stock and have type "sellable"
- sum up the the prices of all those products
- if sum is 0, return nothing, if 1, append "Dollar", else append "Dollars"
Good Parts:
- precise & readable code
- high reusability factor
- small logic pieces
- no need to write too much own code
Bad Parts:
- Takes a while to get the "thinking"
- Sometimes hard to make it work they way you want
- Typings with typescript can be painful
If you want to learn more:
http://randycoulman.com/blog/categories/thinking-in-ramda/
SUMMARY
FP with Ramda
By Dave L.
FP with Ramda
A little introduction to do pracitcal FP n JavaScript with Ramda.
