![Page 1: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/1.jpg)
Dave Bouwman | Software Engineer | ArcGIS Hub & ArcGIS Enterprise Sites
Taming the Beast: Functional Javascript for Sane Applications
![Page 2: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/2.jpg)
wingsofahero/3308105238
About Me
~21+ yrs as a developer15 yrs consultant6 yrs @ ArcGIS Hub
![Page 3: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/3.jpg)
wingsofahero/3308105238
As a consultant…
![Page 4: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/4.jpg)
wingsofahero/3308105238
At Esri… shipping products…
![Page 5: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/5.jpg)
wingsofahero/3308105238
Optimize for maintenance and flexibility
![Page 6: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/6.jpg)
wingsofahero/3308105238
Also, complexity is a thing.
![Page 7: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/7.jpg)
Led me to…
![Page 8: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/8.jpg)
FunctionalProgramming
Led me to…
![Page 9: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/9.jpg)
StyleProgrammingof
![Page 10: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/10.jpg)
1930’s Lambda Calculus
Alonzo Church
![Page 11: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/11.jpg)
Combinatory Logic
Haskell CurryAlonzo Church
![Page 12: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/12.jpg)
System of “computability”
Haskell CurryAlonzo Church
![Page 13: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/13.jpg)
“math functions”
Haskell CurryAlonzo Church
![Page 14: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/14.jpg)
“transform values”
Haskell CurryAlonzo Church
![Page 15: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/15.jpg)
“pure functions”
Haskell CurryAlonzo Church
![Page 16: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/16.jpg)
RobustMaintainable
Software
![Page 17: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/17.jpg)
Many Languages
![Page 18: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/18.jpg)
Pure Functional
LISPHaskellErlangScalaElm
OCamlML
![Page 19: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/19.jpg)
FP Capable
JavaC#
Javascript
![Page 20: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/20.jpg)
Why the Interest now?
Why the interest now?
![Page 21: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/21.jpg)
“wide computers”
![Page 22: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/22.jpg)
pure functions parallelize
![Page 23: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/23.jpg)
List of 1,000,000 things…
![Page 24: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/24.jpg)
output = things.map(pureFn)
![Page 25: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/25.jpg)
Runs across all cores*
![Page 26: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/26.jpg)
Across a whole cluster.
![Page 27: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/27.jpg)
Pure Functional
LISPHaskellErlangScalaElm
OCamlML
![Page 28: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/28.jpg)
24258698@N04/37656086
![Page 29: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/29.jpg)
Let’s talk about js apps
![Page 30: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/30.jpg)
![Page 31: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/31.jpg)
![Page 32: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/32.jpg)
Functional style reduces these risks
![Page 33: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/33.jpg)
![Page 34: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/34.jpg)
wingsofahero/3308105238
With functions…
import {just, whatya, need} from “some-lib”
(ArcGIS-REST-JS is designed around this)
![Page 35: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/35.jpg)
wingsofahero/3308105238
Webpack & Rollup willonly include those functions
(and anything they call)
![Page 36: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/36.jpg)
juan-alogico/10935384913
![Page 37: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/37.jpg)
wingsofahero/3308105238
Functional Programmingis core to React & Angular
![Page 38: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/38.jpg)
24258698@N04/37656086
![Page 39: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/39.jpg)
Avoid Inheritance
Class Guidelines
![Page 40: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/40.jpg)
Except UI Frameworks (React/Angular)
Class Guidelines
![Page 41: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/41.jpg)
Use Composition
Class Guidelines
![Page 42: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/42.jpg)
Factory Functions vs “new”
Class Guidelines
![Page 43: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/43.jpg)
wingsofahero/3308105238
Key Ideas:
Pure FunctionsImmutable Data
Referential TransparencyMany Small Functions
Higher Order Functions
![Page 44: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/44.jpg)
Pure Function
Output depends only on arguments.Zero side -effects
let z = 10;const add = (a,b) => a + b;add(5,3); // 8
![Page 45: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/45.jpg)
Immutable Data
Mutation of shared data is a side -effect.
Return a clone with the changes applied.
Now your function is pure.
![Page 46: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/46.jpg)
Referential Transparency
Program operates the same way if you replace a function call with it’s return value.
let length = add(5,3); let length = 8;
![Page 47: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/47.jpg)
Many Small Functions
We compose many smaller, generic, highly tested functions into larger
more complex functions
![Page 48: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/48.jpg)
Higher Order Functions
Functions that accept or return functions.
const addN = (n) => (x) => add(n, x);const addfive = addN(5);
addfive(10) // 15[1,2,3].map(addFive) // [6,7,8]
![Page 49: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/49.jpg)
Higher Order Functions
Allow us to compose functions
const pipe = (...fns) => x => fns.reduce((y, f) => f(y), x);
doThings = pipe(fn1, fn2, fn3);doThings(someInputs);
![Page 50: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/50.jpg)
Functional 101
![Page 51: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/51.jpg)
![Page 52: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/52.jpg)
![Page 53: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/53.jpg)
“What not how”
![Page 54: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/54.jpg)
We should skip the null…
![Page 55: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/55.jpg)
![Page 56: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/56.jpg)
![Page 57: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/57.jpg)
![Page 58: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/58.jpg)
![Page 59: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/59.jpg)
![Page 60: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/60.jpg)
.reduce(...) is the power move
![Page 61: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/61.jpg)
![Page 62: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/62.jpg)
ExampleApplication
![Page 63: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/63.jpg)
ExampleApplication
![Page 64: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/64.jpg)
40s on Mobile
![Page 65: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/65.jpg)
wingsofahero/3308105238
https://nocotrails.surge.sh
github.com/dbouwman/trail-status-react
![Page 66: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/66.jpg)
Filters
Area
Trails & Status
500ms to first paint8s to fully loaded
![Page 67: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/67.jpg)
NavBar.jsx
Area.jsx
Trail.jsx
App.jsx
500ms to first paint8s to fully loaded
![Page 68: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/68.jpg)
wingsofahero/3308105238
• Query Feature Services• Combine Results• Extract Attributes Hash• Normalize Field Names• Dedupe Segments• Group by Area• Sort by Area and Trail Name• Render
getData(state)
![Page 69: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/69.jpg)
Let’s look at the data…
![Page 70: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/70.jpg)
Different fieldname
nesting
Null meansClosed
![Page 71: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/71.jpg)
Implementation options…
![Page 72: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/72.jpg)
![Page 73: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/73.jpg)
![Page 74: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/74.jpg)
wingsofahero/3308105238
Compose Small Functions
![Page 75: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/75.jpg)
Promise Chain makes it obvious
![Page 76: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/76.jpg)
Generic composition is better
![Page 77: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/77.jpg)
![Page 78: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/78.jpg)
Merge the responses…
![Page 79: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/79.jpg)
![Page 80: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/80.jpg)
Remove nestingOf Attributes
![Page 81: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/81.jpg)
![Page 82: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/82.jpg)
![Page 83: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/83.jpg)
![Page 84: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/84.jpg)
wingsofahero/3308105238
getProp(path, obj, def)
![Page 85: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/85.jpg)
![Page 86: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/86.jpg)
![Page 87: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/87.jpg)
![Page 88: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/88.jpg)
Remove nestingOf Attributes
![Page 89: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/89.jpg)
![Page 90: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/90.jpg)
![Page 91: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/91.jpg)
wingsofahero/3308105238
partial(fn, arg)
![Page 92: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/92.jpg)
![Page 93: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/93.jpg)
![Page 94: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/94.jpg)
NormalizeSchema
![Page 95: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/95.jpg)
![Page 96: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/96.jpg)
![Page 97: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/97.jpg)
![Page 98: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/98.jpg)
wingsofahero/3308105238
maybeAdd(key, val, target)
![Page 99: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/99.jpg)
![Page 100: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/100.jpg)
DedupeRecords
![Page 101: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/101.jpg)
![Page 102: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/102.jpg)
![Page 103: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/103.jpg)
![Page 104: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/104.jpg)
![Page 105: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/105.jpg)
ScrubRows
![Page 106: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/106.jpg)
![Page 107: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/107.jpg)
Group intoAreas
![Page 108: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/108.jpg)
![Page 109: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/109.jpg)
![Page 110: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/110.jpg)
SortyMcSortFace
![Page 111: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/111.jpg)
Sort Areas by groupSort the Entries by name
![Page 112: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/112.jpg)
![Page 113: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/113.jpg)
![Page 114: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/114.jpg)
wingsofahero/3308105238
DONE!
![Page 115: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/115.jpg)
wingsofahero/3308105238
Trade-offs
![Page 116: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/116.jpg)
Piping creates intermediate arrays
Items processed once into final array
![Page 117: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/117.jpg)
![Page 118: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/118.jpg)
Jumping in!
![Page 119: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/119.jpg)
Start with Array.map/reduce/filtercombined with pure functions
![Page 120: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/120.jpg)
Bring in more helpers…
getPropsetProp
cloneObject
![Page 121: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/121.jpg)
Bring in libraries
![Page 122: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/122.jpg)
![Page 123: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/123.jpg)
![Page 124: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/124.jpg)
![Page 125: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/125.jpg)
• Professor Frisby’s Mostly Adequate Guide to Functional Programming (gitbook)
• Composing Software book by Eric Elliot – also on medium)
• So You Want to be a Functional Programmer (medium posts by Charles Scalfani)
• Functional-Light Javascript (book by Kyle Simpson – also on github)
![Page 126: Taming the Beast: Functional JavaScript for Sane ApplicationsTaming the Beast: Functional JavaScript for Sane Applications Author: Esri Subject: 2020 Esri Developer Summit -- Presentation](https://reader031.vdocuments.net/reader031/viewer/2022011822/5ec98221565d3e44ea2a4fd3/html5/thumbnails/126.jpg)
wingsofahero/3308105238
Key Ideas:
Pure FunctionsImmutable Data
Referential TransparencyMany Small Functions
Higher Order Functions