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
JavaScript Promises - Thinking Sync in an Async World
Search
Kerrick Long
February 06, 2014
Programming
20
7.3k
JavaScript Promises - Thinking Sync in an Async World
Presented at the STL Ember.js Meetup on 2014-02-06. Video:
http://youtu.be/wc72cyYt8-c
Kerrick Long
February 06, 2014
Tweet
Share
More Decks by Kerrick Long
See All by Kerrick Long
15 Things You Shouldn't Do In Ember Anymore
kerrick
0
1k
The ECMAScript formerly known as 6
kerrick
0
1.1k
CSS Study Group 1
kerrick
0
1.1k
CSS Study Group 2
kerrick
1
980
Services & Component Collaboration
kerrick
0
730
Donate STL #Build4STL Hackathon Keynote
kerrick
0
280
Donate STL
kerrick
0
800
TDD With Ember.js
kerrick
0
1k
Other Decks in Programming
See All in Programming
Snowflakeで眠ったデータを起こそう!
estie
0
110
educure_カリキュラム生操作マニュアル.pdf
linew_official
0
730
今、知っておきたい! 生成AIエージェントの世界
elith
3
350
見た目から始める生産性向上
ikumatadokoro
7
830
スキーマ駆動開発による品質とスピードの両立 - 私達は何故、スキーマを書くのか
kentaroutakeda
0
170
try! Swift Tokyo 2024のLT枠に採択されたプロポーザルを出すときに考えていたこと
ski
0
350
TYPO3 v13 – The road to LTS: What's new and new APIs
luisasofie_xoxo
0
200
Code Reviews
bkuhlmann
4
890
0→1と1→10の狭間で Javaという技術選定を振り返る/Reflecting on the Decision to Choose Java Between Scaling from 0 to 1 and 1 to 10
jaguar_imo
2
380
新宿ダンジョンを可視化してみた
satoshi7190
2
240
Amazon SQSコンシューマー疎結合への旅 - 出張! #DevelopersIO IT技術ブログの中の人が語る勉強会 #3
quiver
0
230
Rubyでたのしむクリエイティブコーディング/Enjoy Creative coding with Ruby
chobishiba
1
180
Featured
See All Featured
RailsConf & Balkan Ruby 2019: The Past, Present, and Future of Rails at GitHub
eileencodes
125
32k
The MySQL Ecosystem @ GitHub 2015
samlambert
243
12k
A Tale of Four Properties
chriscoyier
151
22k
The Cost Of JavaScript in 2023
addyosmani
16
3.9k
Producing Creativity
orderedlist
PRO
337
39k
Why Our Code Smells
bkeepers
PRO
331
56k
Building Flexible Design Systems
yeseniaperezcruz
319
37k
Sharpening the Axe: The Primacy of Toolmaking
bcantrill
17
1.4k
Dealing with People You Can't Stand - Big Design 2015
cassininazir
357
22k
Java REST API Framework Comparison - PWX 2021
mraible
PRO
18
6.9k
Web Components: a chance to create the future
zenorocha
305
41k
RailsConf 2023
tenderlove
4
540
Transcript
JavaScript Promises Thinking Sync in an Async World then
Kerrick Long Things I make and do Where to find
me online twitter.com/KerrickLong github.com/Kerrick Lead Front-end Developer! at Second Street KerrickLong.com www. meetup.com/STLEmber
try {! console.log(getLatestGrade(getStudent(name)));! }! catch (error) {! logError(error);! }! finally
{! logOut();! }!
try {! console.log(getLatestGrade(getStudent(name)));! }! catch (error) {! logError(error);! }! finally
{! logOut();! }! XMLHttpRequest
getStudent(name, function(student) {! getLatestGrade(student, function(grade) {! console.log(grade);! logOut();! });! });!
var handleError = function(error) {! logError(error);! logOut();! };! getStudent(name, function(error,
student) {! if (error) return handleError(error);! getLatestGrade(student, function(error, grade) {! if (error) return handleError(error);! console.log(grade);! logOut();! });! });!
var handleError = function(error) {! logError(error);! logOut();! };! getStudent(name, {!
error: handleError,! success: function(student) {! getLatestGrade(student, {! error: handleError! success: function(grade) {! console.log(grade);! logOut();! },! })! },! });!
try {! console.log(getLatestGrade(getStudent(name)));! }! catch (error) {! logError(error);! }! finally
{! logOut();! }! Awesome
var handleError = function(error) {! logError(error);! logOut();! };! getStudent(name, {!
error: handleError,! success: function(student) {! getLatestGrade(student, {! error: handleError! success: function(grade) {! console.log(grade);! logOut();! },! })! },! });! Awkward.
getStudent(name)! .then(getLatestGrade)! .then(console.log)! .catch(logError)! .then(logOut)! ;! Promises
None
Promise Basics
Promise Basics Consuming Promises
Promise Basics Consuming Promises Creating Promises
Promise Basics Consuming Promises Creating Promises Advanced Techniques
Promise Basics
Getting Promises
None
RSVP.js Q.js • Bluebird
RSVP.js Q.js • Bluebird Promises/A+
Promise Guarantees
Always Async
Always Async Returns a Promise
Always Async Returns a Promise Handled Once
Always Async Returns a Promise Handled Once Then’able
Promise States
Promise States Pending Fulfilled Rejected
Promise States Pending Fulfilled Rejected } Settled
Promise States Pending Fulfilled Rejected
Promise States Pending Fulfilled Rejected Value Reason
Promise States Pending Fulfilled Rejected Return Value Thrown Exception
Consuming Promises
Promise Prototype Methods
getJSON('/comments')! .then(onFulfilled, onRejected) Promise.prototype.then
getJSON('/comments')! .then(function(comments) {! if (comments) return 'Good'! else throw new
Error('Bad')! }, function(reason) {! // handle getJSON errors! }) Promise.prototype.then
getJSON('/comments')! .then(fulfillOne, rejectOne)! .then(fulfillTwo)! .then(null, rejectTwo) Promise.prototype.then
getJSON('/comments')! .then(fulfillOne, rejectOne)! .then(fulfillTwo)! .then(null, rejectTwo) Promise.prototype.then THROW
getJSON('/comments')! .then(fulfillOne, rejectOne)! .then(fulfillTwo)! .then(null, rejectTwo) Promise.prototype.then THROW
getJSON onFulfilled onRejected getJSON onFulfilled onRejected
getJSON('/comments') // waiting...! .then(extractFirstId)! .then(getCommentById) // waiting...! .then(showComment) Promise.prototype.then
var promise = getJSON('/comments');! somethingElse();! promise.then(onFulfilled, onRejected); Promise.prototype.then
getJSON('/comments')! .then(null, onRejected) Promise.prototype.catch
getJSON('/comments')! .catch(onRejected) Promise.prototype.catch
Promise Static Methods
Promise.cast('Hi you!')! .then(onFulfilled, onRejected) Promise.cast
Promise.cast(seededRandom(42))! .then(onFulfilled, onRejected) Promise.cast
Promise.cast($.ajax(config))! .then(onFulfilled, onRejected) Promise.cast
$.ajax(config)! .then(onFulfilled, onRejected)
$.ajax(config)! .then(onFulfilled, onRejected) Lies, all LIES!
Promise.cast($.ajax(config))! .then(onFulfilled, onRejected) Promise.cast
var promises = [ getJSON('/a'),! getJSON('/b'), getJSON('/c') ]! ! Promise.all(promises)!
.then(allFulfilled, firstRejected) Promise.all
var promises = [ getJSON('/a'),! 'Hi you!', 42, getJSON('/c') ]!
! Promise.all(promises)! .then(allFulfilled, firstRejected) Promise.all
var promises = [ saveTo(server1),! saveTo(server2), saveTo(server3) ]! ! Promise.race(promises)!
.then(firstFulfilled, firstRejected) Promise.race
Creating Promises
new Promise()
function() {! var name = prompt('Your name?')! if (!name)! throw
new Error('Rude user!')! else! return name! } new Promise()
new Promise(function(fulfill, reject) {! var name = prompt('Your name?')! if
(!name)! throw new Error('Rude user!')! else! return name! }) new Promise()
new Promise(function(fulfill, reject) {! var name = prompt('Your name?')! if
(!name)! reject(new Error('Rude user!'))! else! fulfill(name)! }) new Promise()
Shortcuts
new Promise(function(fulfill, reject) {! fulfill(something)! }) Promise.resolve()
new Promise(function(fulfill, reject) {! fulfill(something)! })! Promise.resolve(something) Promise.resolve()
new Promise(function(fulfill, reject) {! reject(something)! }) Promise.reject()
new Promise(function(fulfill, reject) {! reject(something)! })! Promise.reject(something) Promise.reject()
Advanced Techniques
this.get('name') // 'Kerrick'! ! getJSON('/comments')! .then(function(comments) {! this.get('name') // throws!
}) this and bind()
this.get('name') // 'Kerrick'! var self = this! getJSON('/comments')! .then(function(comments) {!
self.get('name') // 'Kerrick'! }) this and bind()
this.get('name') // 'Kerrick'! ! getJSON('/comments')! .then(function(comments) {! this.get('name') // 'Kerrick'!
}.bind(this)) this and bind()
getJSON('/comments')! .then(function(comments) {! throw new Error('Hello?')! }) Absorbed Rejections
getJSON('/comments')! .then(function(comments) {! throw new Error('Hello?')! })! .catch(console.error.bind(console)) Absorbed Rejections
getStudent(name) // <Promise>! .then(getLatestGrade)! .then(log)! .catch(logError)! .then(logOut) Promise-aware Functions
log(getLatestGrade(getStudent(name)))! .catch(logError)! .then(logOut) Promise-aware Functions
function getLatestGrade(promise) {! return Promise.cast(promise)! .then(function(value) {! // getLatestGrade Logic!
})! } Promise-aware Functions