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14 Elm Can Make You A Better JavaScript Developer.md

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Elm Can Make You A Better JavaScript Developer

Jamison Dance (@jergason)

  • average JavaScript payload grew from 100kb to 400kb from 2014 to 2015

  • base assumption of all browser development: apps are developed in JavaScript

  • rethink best practices: Elm

    • functional programming language
    • runs in the browser
    • compiles to JavaScript

  • undefined is not a function

     function foo(num) {
 	if (num > 10) {
 		return 'bar'
 	}
 }
 console.log(foo(1).toUpperCase())
    • runtime errors happen in JavaScript
    • error tracking developed in/for JavaScript (track:js, raygun.io, ...)
    • error preventing developed in/for JavaScript (eslint, flow, typescript, ...)
    • plug-in type systems have a problem: they can be plugged off

  • Elm

     foo : Int -> Maybe String
 foo num =
 	if num > 10 then Just 'bar'
 	else Nothing
 
 bar num =
 	case foo num of
 		Just str ->
 			String.toUpper str
 		Nothing ->
 			0
    • static type system => no runtime errors
    • algebraic data types
     type Maybe a = Just a | Nothing

  • application architecture

    • React: tree of components, data flows down, actions flow up
    • Elm
      • only stateless functions
      • only immutable data
      • messages to pass data around the application (flux is based on elm)
      • decisions are made on the language level => no Elm fatigue

  • constraints vs guidelines – if you write elm the probability is higher that you write a good program

  • caveats

    • smaller community
    • "one correct way"
    • server rendering not easy
    • does better when it runs everything
    • still in the early days ("maybe production ready")