Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Elements of Functional Programming in JS
Search
Adam Stankiewicz
May 27, 2014
Programming
2
150
Elements of Functional Programming in JS
Lightning talk from Meet.js Wrocław.
Adam Stankiewicz
May 27, 2014
Tweet
Share
More Decks by Adam Stankiewicz
See All by Adam Stankiewicz
LinemanJS
sheerun
0
110
Consuming and Packaging of Web Components
sheerun
4
410
Promises/A+
sheerun
5
400
Other Decks in Programming
See All in Programming
GitHub Copilot and GitHub Codespaces Hands-on
ymd65536
2
150
PHP 8.4の新機能「プロパティフック」から学ぶオブジェクト指向設計とリスコフの置換原則
kentaroutakeda
2
950
AI Agent 時代のソフトウェア開発を支える AWS Cloud Development Kit (CDK)
konokenj
3
270
Deep Dive into ~/.claude/projects
hiragram
14
2.6k
A full stack side project webapp all in Kotlin (KotlinConf 2025)
dankim
0
120
レベル1の開発生産性向上に取り組む − 日々の作業の効率化・自動化を通じた改善活動
kesoji
0
240
初学者でも今すぐできる、Claude Codeの生産性を10倍上げるTips
s4yuba
16
12k
型で語るカタ
irof
0
200
What's new in AppKit on macOS 26
1024jp
0
110
ご注文の差分はこちらですか? 〜 AWS CDK のいろいろな差分検出と安全なデプロイ
konokenj
2
110
NPOでのDevinの活用
codeforeveryone
0
860
ふつうの技術スタックでアート作品を作ってみる
akira888
1
900
Featured
See All Featured
Facilitating Awesome Meetings
lara
54
6.4k
Typedesign – Prime Four
hannesfritz
42
2.7k
Into the Great Unknown - MozCon
thekraken
40
1.9k
Docker and Python
trallard
44
3.5k
The Art of Delivering Value - GDevCon NA Keynote
reverentgeek
15
1.5k
Responsive Adventures: Dirty Tricks From The Dark Corners of Front-End
smashingmag
251
21k
The MySQL Ecosystem @ GitHub 2015
samlambert
251
13k
Site-Speed That Sticks
csswizardry
10
690
Why You Should Never Use an ORM
jnunemaker
PRO
58
9.4k
Adopting Sorbet at Scale
ufuk
77
9.5k
Automating Front-end Workflow
addyosmani
1370
200k
XXLCSS - How to scale CSS and keep your sanity
sugarenia
248
1.3M
Transcript
Elements of Functional Programming in JavaScript
What is functional programming? No generally accepted definition, but: •
Style of building computer programs • Avoids state and mutable data • Functions as arguments and results
Benefits of functional programming • More concise, readable code •
Confident refactor, better reasoning • Better concurrency? • Performance (function inlining)
JS has some functional elements • First class functions •
Anonymous functions (lambdas) • ???
JS lacks many functional elements • Tail call optimization •
Pattern matching • Forced immutability (type system) • No standard methods for FP (IE <=8) ◦ Array#forEach, Array#map, Array#filter, etc...
Libraries for FP in JavaScript • Underscore • Lo-Dash •
Mout.js (for Node.js)
Short map syntax var characters = [ { 'id': 1,
'name': 'barney', 'age': 26 }, { 'id': 2, 'name': 'fred', 'age': 30 } ]; _.map(characters, function(c) { return c['name']; }) // ['barney', 'fred'] _.map(characters, 'name') // ['barney', 'fred']
Short filter syntax var characters = [ { 'id': 1,
'name': 'barney', 'age': 26 }, { 'id': 2, 'name': 'fred', 'age': 30 } ]; _.filter(characters, function(c) { return c.age == 30; }) // [{ 'id': 2, 'name': 'fred', 'age': 30 }] _.filter(characters, { age: 30 }) // [{ 'id': 2, 'name': 'fred', 'age': 30 }]
General pattern // function(e) { return e['foo']; } // 'foo'
_.sortBy(characters, 'name') // function(e) { return e['foo'] == bar; } // { 'foo': bar } _.every(characters, { 'name': 'barney' })
GroupBy var words = ['one', 'two', 'three'] _.groupBy(words, 'length'); //
{ '3': ['one', 'two'], '5': ['three'] }
IndexBy var users = [ { 'id': 100, 'name': 'Adam'
}, { 'id': 200, 'name': 'Ala' } ]; var indexedUsers = _.indexBy(users, 'id') indexedUsers[100] // { 'id': 100, 'name': 'Adam' } indexedUsers[200] // { 'id': 100, 'name': 'Ala' }
Find var users = [ { 'id': 100, 'name': 'Adam'
}, { 'id': 200, 'name': 'Ala' } ]; _.find(users, { 'id': 100 }); // { 'id': 100, 'name': 'Adam' }
max, min var characters = [ { 'name': 'barney', 'age':
26 }, { 'name': 'fred', 'age': 30 } ]; _.max(characters, 'age') // { 'name': 'fred', 'age': 30 } _.min(characters, 'age') // { 'name': 'barney', 'age': 26 }
reduce var numbers = [1, 2, 3]; _.reduce(numbers, function(sum, element)
{ return sum + element }); // 6
Composing functions var characters = [ { 'name': 'barney', 'age':
26 }, { 'name': 'fred', 'age': 30 }, // ... ]; var ages = _.map(characters, 'age'); // [26, 30] _.reduce(ages, function(a, b) { return a + b }); // [56]
Composing functions var characters = [ { 'name': 'barney', 'age':
26 }, { 'name': 'fred', 'age': 30 }, // ... ]; _(characters) .map('age') .reduce(function(a, b) { return a + b; });
Composing functions var characters = [ { 'name': 'barney', 'age':
26 }, { 'name': 'fred', 'age': 30 }, // ... ]; _(characters) .map('age') .reduce(function(a, b) { return a + b; });
Other features • Set operations (difference, union, intersection) • every,
some, reject, countBy, contains • clone, extend, defaults, merge, mapValues • delay, defer, memoize, once, throttle • now, random, uniqueId, template
Promises A+ • Pattern for running async code • Allows
for return in callbacks • Safely handles exceptions in callbacks • Allows for try/catch -like behavior • Chaining of callbacks, parallel execution promise.then(onSuccess, onFailure)
Promises A+ $http.get('/users/1').then(function(user) { return $http.get("/users/posts"); }).then(function(post) { return render(post);
}).catch(function(reason) { console.log(reason); });
Dzięki