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JavaScript Bootcamp 2019
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Recruit Technologies
June 24, 2019
Technology
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45k
JavaScript Bootcamp 2019
2019年度リクルート新人ブートキャンプ エンジニアコースの講義資料です
Recruit Technologies
June 24, 2019
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Transcript
JavaScript Bootcamp 2019 2019, 12th April @ Recruit Technologies Kento
TSUJI @maxmellon
ࣗݾհ • Github: @maxmellon • Twitter: @maxmellon_9039 • ϦΫϧʔτςΫϊϩδʔζ 18
৽ଔೖࣾ • ࠷ۙ Apex ͬͯΔΑʙ
Δ͜ͱɺΒͳ͍͜ͱ Δ͜ͱ Βͳ͍͜ͱ ɾ ɾ جຊతͳه๏ ɾ ΫϥΠΞϯτ࣮ ɾ αʔόʔ࣮
ɾ ςετίʔυ࣮ ɾ σϓϩΠ ޙͰݟ͓ͯ͘ͱྑͦ͞͏ͳͷ https://github.com/asciidwango/js-primer js-primer Ͱݕࡧ
ϑϩϯτΤϯυΤϯδχΞͱ JavaScript • ϦΫϧʔτςΫϊϩδʔζͷ “ϑϩϯτΤϯυΤϯδχΞ” ͷఆٛͯ͘ਂ͍ • HTML/CSS/JSΛ۶ࢦͯ͠ΫϥΠΞϯτΛ ࡞Δ͚ͩͰͳ͍
• ϑϩϯτΤϯυͷͨΊͷαʔόʔύϑΥʔϚϯ ενϡʔχϯάɺϢʔβϏϦςΟ্ͳͲ༷ʑ
ϦΫϧʔτͷ ϑϩϯτΤϯδχΞͬͯ ͳʹ͢Δͷʁ
ࣗͷ߹
ۀ༰ • Airγϑτͱ͍͏αʔϏεͷ ϑϩϯτΤϯυΛ։ൃ͍ͯ͠Δ • ࠷ۙओʹύϑΥʔϚϯενϡʔϯϯά • ώΞϦϯάߦͬͨΓ͢Δ͠ Ϣʔβʔମݧ࠷େԽͷͨΊʹͳΜͰΔ
Airγϑτ ͱ
None
None
None
"JSγϑτར༻͍ͯ͠ΔͷͰ͕͢ Ξοϓσʔτ͕͔͋ͬͯΒ ͘͢͝ॏ͍ΜͰ͢ΑͶʜ Ͳ͏ʹ͔ͯ͠ ૣ͘ͳΒͳ͍Ͱ͠ΐ͏͔ʁ ͳΔ΄Ͳʜ ࣗͷύιίϯ͕ѱ͍ͷͰ͠ΐ͏͔ʁ ΫϥΠΞϯτ ΅͘ ↓
͋Δ
࣮ࡍʹݟʹߦ͘ͷࣄ
- ͍ݪҼαʔόʔͰͳ͔ͬͨ - ΫϥΠΞϯτͷPC͕εϖοΫͩͬͨ - ։ൃऀʹൺͯεϖοΫͳPC͕ଟ͘ར༻͞Ε͍ͯΔ ݹ͍ ͍ ฉ͍ͯΈΔͱ
• γϑτͷྔ͕༧ΑΓଟ͔ͬͨ • άϧʔϓػೳͰళฮͷछผΛ͍ͯͨ͠ • HTMLͷඳըΑΓJavaScriptͷ࣮ߦ͕͔ͬͨ ϘτϧωοΫͷ΄ͱΜͲ͕ +BWB4DSJQUͷ࣮ߦ ˋ 9.8ඵ
1.1ඵ 3.5ඵ 0.1ඵ JavaScriptͷ࣮ߦ HTMLͷඳը CSSͷద༻ ͦͷଞ ࣮ࡍʹ๚͢Δͱ
ώΞϦϯάͱσʔλ͔Β ௐࠪͯ͠ϘτϧωοΫΛಛఆ
ͨ͘͞ΜͷΛ ಛఆɺղܾ ϝϯόʔζϒϩάʹ ܝࡌࡁΈ
13.5 ඵ͔Β 2.6ඵʹվળ After Before 2.6ඵ 13.5ඵ ౦ژNodeֶԂࡇ ‘18 HTML5
Conferenceʹͯ հ 11ඵ ແବΛΧοτ ඳըྃ ඳըྃ ܭࢉϦιʔεͷऔಘ ݁Ռ 50%ͷϢʔβʔͰ 5.0ඵ͔Β1.5ඵʹऩ·ΔΑ͏ʹ
ߴ͍ٕज़ͱ ͍ܰϑοτϫʔΫ Λࢦ͕ͯ͠Μͬͯ·͢
ࠓͷྲྀΕ 1. JavaScript ΛͱΓ͍͋ͣ৮ͬͯΈΔ 2. JavaScript Ͱ؆୯ͳΞϓϦέʔγϣϯΛ ࡞ͬͯΈΔ
৮ͬͯΈΑ͏
ͱΓ͋͑ͣಈ͔ͯ͠ΈΔ
$ node -v v11.10.1 $ node > // ͜͜ͰJavaScriptΛ࣮ߦ͢Δ͜ͱ͕Ͱ͖·͢ undefined
> 1 + 1; 2 > var test = "hoge"; undefined > test 'hoge' > function sample() { ... var num = 5; ... return num; ... } undefined > sample() 5
Hello World
Hello World
$ touch helloworld.js $ code helloworld.js $ node helloworld.js Hello
World 01 02 console.log('Hello World');
JavaScript ͷ͋Ε͜Ε • Variable declaration • function • object •
class • promise
Variable declaration
Variable declaration είʔϓ ࠶ೖ Մมෆม DPOTU MFU WBS
Variable declaration είʔϓ ࠶ೖ Մมෆม DPOTU ϒϩοΫ ෆՄ Մม MFU
ϒϩοΫ Մೳ Մม WBS ؔ Մೳ Մม
είʔϓ let a = 1; if (a === 1) {
let a = 2; console.log(a); // 2 } console.log(a); // 1 ϒϩοΫ var a = 1; if (a === 1) { var a = 2; console.log(a); // 2 } console.log(a); // 2 ؔ (άϩʔόϧ)
࠶ೖ ͱ ՄมɺෆՄม ؔ (άϩʔόϧ) const ࠶ೖෆՄೳ const a
= 1 a = 2 Uncaught SyntaxError: Identifier 'a' has already been declared const ࠶ೖ͕Ͱ͖ͳ͍͚ͩͰॻ͖͑ΕΔ const a = [] a.push(1) console.log(a) // [1] a.pop() console.log(a) // []
ͲΕ͔͍͍ͭ͑ͷʁ • ࠶ೖϩδοΫΛෳࡶԽͤ͞Δ͜ͱ͕ଟ͍ → جຊతʹ const • Ͳ͏ͯ͠࠶ೖ͍ͨ͠ͱ͖ ˠ let
• var lint Ͱېࢭ͢Δ͜ͱଟ͍
function
ؔએݴͱؔࣜ function Greeting() { console.log('hello') } const Greeting = function()
{ console.log('hello') } • syntax Α͘ࣅ͍ͯΔ • એݴ ר্͖͕͛ى͖Δ
ؔࣜͱΞϩʔϑΝϯΫγϣϯ const Greeting = function() { console.log('hello') } const Greeting
= () => { console.log('hello') } • ͔͚͘Δ • ΞϩʔϑΝϯΫγϣϯ this Λଋറ͠ͳ͍ ؔࣜͱΞϩʔϑΝϯΫγϣϯͷҧ͍ ͔͚͘ΔͷͰΞϩʔϑΝϯΫγϣϯΛ͏໘ଟ͍
JavaScript ʹ͓͚Δ this • ΞϩʔؔҎ֎ͷؔ • Ϋϥε • ΦϒδΣΫτ •
bindؔ thisͷίϯςΩετ͕มΘΔ໘ ҰൠతͳݴޠͱUIJT͕ҧ͏ͱݴΘΕΔͷ UIJTͷίϯςΩετ͕มΘͬͯ͠·͏͔Β https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Operators/this
ΞϩʔϑΝϯΫγϣϯ const foo = (a, b) => { return a
+ b } ΞϩʔϑΝϯΫγϣϯͰ͕ࣜҰͭͷͱ͖ʹݶΓϒϩοΫΛলུ͔͚ͯ͠Δ const foo = (a, b) => a + b // ·ͨ const foo = (a, b) => ( a + b ) ϒϩοΫΛলུͨ͠߹ɼͦͷࣜΛ࣮ߦͨ݁͠Ռ͕ return ͞ΕΔ
Ҿ function doSomeThing(a, b, c = 0) { console.log('a %o',
a) console.log('b %o', b) console.log('c %o', c) } doSomeThing(1, 2) // a 1 // b 2 // c 0 doSomeThing(...[1, 2, 3]) // a 1 // b 2 // c 3 function doSomeThing(...args) { console.log('args %o', args) } doSomeThing(1, 2, 3) // args [1, 2, 3] doSomeThing([1], 2, 3) // args [[1], 2, 3] doSomeThing(...[1, 2, 3]) // args [1, 2, 3] σϑΥϧτҾ Մม
object
Objectͱ • σʔλͱػೳͷू߹ • ϓϩύςΟͱϝιου͕ઃఆͰ͖Δ
ྫ const person = { name: ['Bob', 'Smith'], age: 32,
gender: 'male', interests: ['music', 'skiing'], bio() { alert(`${this.name.join(' ')} is ${this.age} years old.`); }, greeting() { alert('Hi! I\'m ' + this.name[0] + '.'); } };
objectʹ͓͚Δmethod const person = { greeting() { alert('Hi!'); } };
const person = { greeting: function() { alert('Hi!'); } }; • ӈͷํ͕͔͚͘Δ • ҙຯશ͘ಉ͡
const person = { _age: 25, _name: 'maxmellon', get age()
{ return this._age; }, get name() { return this._name; } }; ObjectͰήολʔηολʔ͕͑Δ • private ͕ͳ͔ͬͨ࣌ ͜͏͍͏ײ͡ͰΧϓηϧԽͯͨ͠
Object Λ࡞Δ const age = 23 const name = 'Kento
TSUJI' const parson = { age: age, name: name, } ͜Ε ͜͏͔͚Δ const age = 23 const name = 'Kento TSUJI' const parson = { age, name, }
Object ͔ΒΛऔΓग़͢ const age = parson.age const name = parson.name
͜Ε const { age, name } = parson ͜͏͔͚Δ
Object Λίϐʔ͢Δ const copied = { ...parson } const copied
= Object.assign({}, parson) Shallow Copy جຊతʹͬͪ͜ͷॻ͖ํͰॻ͘ Object ͕ωετͨ͠ͱ͖ɼ ࢠͷObjectͷࢀরมԽ͠ͳ͍͜ͱʹҙ ͜ΕΛάάΔͱ͖ `spread operator` ͱ͔ εϓϨουԋࢉࢠͱ͔
Object ΛϚʔδ͢Δ const a = { foo: 1, hoge: 'a',
} const b = { hoge: 'b', poge: 2, } const merged = { ...a, ...b } { foo: 1, hoge: 'b', poge: 2, } ϚʔδͰ `spread operator` ͕͑Δ
class
ΫϥεએݴͱΫϥεࣜ class Hoge { method() { } } const
Hoge = class { method() { } } • Ϋϥεએݴ ר্͖͕͛ى͖ͳ͍ const Hoge = class Hoge { method() { } } Ϋϥεએݴ Ϋϥεࣜ ໊લ͖Ϋϥεࣜ
class Rectangle { constructor(height, width) { this.height = height; this.width
= width; } // ήολʔ get area() { return this.calcArea(); } // ϝιου calcArea() { return this.height * this.width; } } const square = new Rectangle(10, 10); console.log(square.area); // 100 square.height = 20; // 'aaaa' https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Classes ϝιουఆٛ
Tips • JavaScriptprototypeϕʔεͷݴޠ • class prorotypeͱObjectΛͬͨ දݱΛ؆ܿʹΘ͔Γ͘͢ॻͨ͘Ίͷͷ • ͳͷͰ͍ΘΏΔΠϯελϯεϝιου
AnyClass.ptototype.method ͷΑ͏ʹදݱ͢Δ ↑ ͜Ε new AnyClass().method() • ελςΟοΫؔAnyClass.staticMethod
༨ஊ private class field
ϞμϯͳϒϥβͰprivate field ͕͑Δ • ϨΨγʔϒϥβͰ͏ʹ transpile ͳͲͷϓϦϓϩηε͕ඞཁ https://github.com/tc39/proposal-private-fields/blob/master/OLD_README.md class Point
{ #x = 0; #y = 0; constructor(x = 0, y = 0) { this.#x = +x; this.#y = +y; } get x() { return this.#x } set x(value) { this.#x = +value } get y() { return this.#y } set y(value) { this.#y = +value } }
ϞμϯͳϒϥβͰprivate field ͕͑Δ • ϨΨγʔϒϥβͰ͏ʹ transpile ͳͲͷϓϦϓϩηε͕ඞཁ https://github.com/tc39/proposal-private-fields/blob/master/OLD_README.md class Point
{ #x = 0; #y = 0; constructor(x = 0, y = 0) { this.#x = +x; this.#y = +y; } get x() { return this.#x } set x(value) { this.#x = +value } get y() { return this.#y } set y(value) { this.#y = +value } }
ಉظ / ඇಉظ
͠ඇಉظ͕ͳ͔ͬͨΒͲ͏ͳΔ͔ • αʔόʔ͔ΒσʔλΛड͚औΔ·Ͱ ଞͷૢ࡞͕Ͱ͖ͳ͍ • ΫϦοΫ͢Δͱϒϥβ͕ݻ·Δ • ॲཧ͕Ұ͔ͭͣͭ͠Ͱ͖ͳ͍
callbackʹΑΔඇಉظ taskA(() => { taskB(() => { taskC(() => {
… }) }) }) ͲΜͲΜωετ͕ਂ͘ͳ͍ͬͯͬͯ͠·͏
promise
promise new Promise((resolve, reject) => { asynchronizedTask((err, result) => {
if (err) reject(err) resolve(result) }) }).then(res => console.log(res)) .catch(err => console.error(err)) • ඇಉظॲཧͷநԽ • then Ͱ ޭͨ͠ͱ͖ͷϋϯυϥΛ ༩͢Δ ৽͍͠PromiseΛฦ͢ (ݫີʹࣦഊϋϯυϥՃͰ͖Δʣ • catch Ͱ ࣦഊϋϯυϥͷίʔϧόοΫΛ༩͢Δ
taskA(() => { taskB(() => { taskC(() => { …
}) }) }) taskA() .then(() => taskB()) .then(() => taskC()) callbackΑΓΘ͔Γ͘͢ॻ͘͜ͱ͕Ͱ͖Δ
promise QSPNJTF UIFO IBOEMFS UIFO IBOEMFS DBUDI PO3FKFDUJPO
FSSPSIBOEMJOH QSPNJTF UIFO IBOE UIFO IBOE DBUDI PO3FKF ػঢ়ଶ ޭ ࣦഊ promise͕ࣦഊͨ͠ͱ͖ thenͷୈೋҾͷhandlerͰྫ֎͕ग़ͨͱ͖ return return ޭ ࣦഊ thenͷϋϯυϥඞͣPromiseΛฦ͢ͷͰ chainͰ͖Δ chainͰ͖Δ
example new Promise((resolve) => { // 1ඵޙʹ ୈ1ҾͷؔΛ࣮ߦ͢Δ setTimeout(() =>
resolve(1), 1000) }).then((res) => { console.log(res) return res + 1 }).then((res) => { console.log(res) return res + 1 }).then((res) => { console.log(res) return res + 1 }) ࣮ߦ͢ΔͱͲΜͳϩάग़ྗ͞ΕΔʁ
fetch API const url = 'https://hacker-news.firebaseio.com/v0/item/2921983.json? print=pretty' fetch(url) .then(resp =>
resp.json()) .then(resp => console.log(resp)) • ྫ͑ɼhacker news ͷ API Λୟ͘ͱ͢Δ { "by" : "norvig", "id" : 2921983, "kids" : [ 2922097, 2922429, 2924562, 2922709, 2922573, 2922140, 2922141 ], "parent" : 2921506, "text" : "Aw shucks, guys ... you make me blush with your compliments.<p>Tell you what, Ill make a deal: I'll keep writing if you keep reading. K?", "time" : 1314211127, "type" : "comment" }
async / await
async function function resolveAfter2Seconds() { return new Promise(resolve => {
setTimeout(() => { resolve('resolved'); }, 2000); }); } async function asyncCall() { console.log('calling'); const result = await resolveAfter2Seconds(); console.log(result); // expected output: 'resolved' } ಉظؔͷΑ͏ʹPromiseΛѻ͏
const doSomeThing = () => { taskA() .then(() => taskB())
.then(() => taskC()) } callbackΑΓΘ͔Γ͘͢ॻ͘͜ͱ͕Ͱ͖Δ const doSomeThing = async () => { await taskA() await taskB() await taksC() }
ԋश
४උ $ npm install @recruit-tech/javascripting -g $ javascripting ↑ ͜ΕΛ࣮ߦ
↓ Έ͍ͨͳը໘͕ͰΕ OK
ຊޠͷม͑ํ
ΨϯΨϯ ਐΊͪΌ͍ͬͯͩ͘͞ (1h ΄ͲऔΓ·͢)
ޙ
ԋश 1. JavaScript ΛͱΓ͍͋ͣ৮ͬͯΈΔ 2. JavaScript Ͱ؆୯ͳΞϓϦέʔγϣϯΛ ࡞ͬͯΈΔ
ࠔͬͨͱ͖ • ҰൠతͳهࣄͷલʹυΩϡϝϯτΛಡΉบΛ ͚ͭ·͠ΐ͏ • ͠OSSΛར༻͍ͯ͠ΔͷͰ͋Εɺ ιʔείʔυಡΉΑ͏ʹҙࣝ͠·͠ΐ͏ • ࠓճͷ߹ɺMDN͕࠷ࢀߟʹͳΔͱ ͓͍·͢
ex. JavaScript ͔Β DOMΛ࡞Γ͍ͨ
͜͜Ͱ͑ͦ͏ͳAPI • Document.createElement https://developer.mozilla.org/ja/docs/Web/API/Document/createElement • Document.querySelector https://developer.mozilla.org/ja/docs/Web/API/Document/querySelector • Array.prototype.forEach https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach
• Array.prototype.map https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/Array/map
JavaScript͔ΒDOMΛૢ࡞͢Δ • DOMπϦʔͷ࡞ํ๏ https://developer.mozilla.org/ja/docs/Web/API/Document_Object_Model/How_to_create_a_DOM_tree
0. ༻ҙ • https://github.com/MaxMEllon/todo-mvc/ Λfork • git clone • npm
install • npm start • ϒϥβͰ http://localhost:3000 ʹΞΫηεʂ
1. APIΛઃܭ͢Δ • create (GET) read (POST) update (PATCH) delete
(DELETE) ͷ4ͭ • read TODO Λશ݅औಘ • TODO ໊લͱ͔ྃͨ͠ Ͳ͏͔ͷεςʔλε͔Βߏ ͻͱ·ͣ Read ͚ͩ Agreed Λͬͯ ઃܭͯ͠ΈΑ͏
2. API͔ΒTODOҰཡΛඳը͢Δ ͖ͬ͞࡞ͬͨ agreed ͔Βऔಘʂ
3. Form͔ΒจࣈྻΛೖྗͯ͠TODOΛ ࡞Ͱ͖ΔΑ͏ʹ͢Δ
4. TODOΛྃঢ়ଶʹͰ͖ΔΑ͏ʹ͢Δ (API௨৴ࠐͰ)
5. TODOΛআͰ͖ΔΑ͏ʹ͢Δ
6. TODOͷDONEʹͳͬͨ݅Λ͑Δ
7. Server Λ࣮͢Δ
Φϓγϣφϧͳ՝ • TODOͷ໊લΛฤूͰ͖ΔΑ͏ʹͯ͠ΈΑ͏ • σβΠϯΛม͑ͯΈΑ͏ • MVVMFluxͰॻ͖ͯ͠ΈΑ͏ • WebComponents Ͱॻ͖ͯ͠ΈΑ͏