DEV Community

Pattern-Match your JavaScript with Z

K on February 20, 2019

Cover image by Dennis Skley on Flickr Functional programming techniques seem to be rather popular these days. People are using monads in JavaScrip...

Read full post

JavaScript Joel • Feb 20 '19

This is incredible. I have a lot of questions regarding how this is done. I use Ramda's cond quite a bit. But I really like this syntax.

I'm curious to see how this works when minified. I believe it is using some type of reflection.

K • Feb 20 '19

It seems to use a package called js-function-reflector which transforms a function object to it's string representation and parses it again.

github.com/arrizalamin/js-function...

halcaponey • Feb 21 '19

and js-function-reflector uses the toString() method availaible on functions

JavaScript Joel • Feb 21 '19

the toString()

That doesn't seem like it would work for minified code as the parameter names would be uglified.

K • Feb 21 '19

It works as long as you don't compile the default arguments to ES5.

JavaScript Joel • Feb 20 '19

One limitation I see is something like this is not possible:

import allPass from 'mojiscript/logic/allPass'
import cond from 'mojiscript/logic/cond'

const isFizz = num => num % 3 === 0
const isBuzz = num => num % 5 === 0
const isFizzBuzz = allPass ([ isFizz, isBuzz ])

const fizziness = cond ([
  [ isFizzBuzz, 'FizzBuzz' ],
  [ isFizz, 'Fizz' ],
  [ isBuzz, 'Buzz' ],
  [ () => true, x => x ]
])

fizziness(1) //=> 1
fizziness(3) //=> 'Fizz'
fizziness(5) //=> 'Buzz'
fizziness(15) //=> 'FizzBuzz'

Anwar • Feb 20 '19

Very interesting, I would use it mostly to do validation. Looking forward to see what it becomes in the future.

K • Feb 20 '19

Yes, I think the type-checking is the most practical feature of it, if it's exhaustive it could prevent many typical JavaScript bugs :)

Matt Del Signore • Feb 20 '19

Yeah, in functional languages it usually replaces conditionals but javascript has a plethora of them. This is super cool though.

Anwar • Feb 20 '19

Absolutely agree, I use Joi but it still seems not "natural enough" for me, always thought Javascript diserved something better. Here you go :)

maxdevjs • Oct 13 '19

Life's filling up with more and more z and z and... Good catch, did not know about this lib :)

Comment deleted

K • Feb 23 '19

Glad, you like it :)