Callback to Promise and beyond

1. $BMMCBDL
   UP
   1SPNJTF
   BOE
   CFZPOE
   
   d
   1SPNJTFԽ͚ͩͰ͸ऴΘΒͳ͍
   d ೥݄೔
   ؔ੢/PEFֶԂ
   ࣌ݶ໨
   Ϡϑʔגࣜձࣾɹ܀ࢁଠر
2. ࣗݾ঺հ ܀ࢁ
   ଠرʢ!"KJEPʣ
   Ϡϑʔגࣜձࣾ
   ›
   /PEFKT
   ࠇଳ
3. w $BMMCBDLΛ1SPNJTFԽ͢Δํ๏
   w $BMMCBDLΛ1SPNJTFԽͨ͠ޙʹ࢒Δ՝୊
   w ੑೳ
   
   ›
   
   ݱ୅తͳϑϩʔ੍ޚ͸ߴ଎ͳͷ͔ʁ
   w ετϦʔϜରԠ
   
   ›
   
   4USFBNΛϑϩʔ੍ޚʹͲ͏૊ΈࠐΉʁ
   w Τϥʔॲཧ
   
   ›
   
   ඇಉظॲཧͷελοΫτϨʔε͸Ͳ͏ݟ͑Δʁ ಺༰
4. /PEFKTʹ͓͚Δඇಉظॲཧͱϑϩʔ੍ޚͷྺ࢙ "TZOD
   UZQF /PEF
   WFSTJPO  $BMMCBDL  3FNPWF
   QSPNJTFT W  BTZOD
   OQN  CMVFCJSE
   OQN
   
   2
   OQN  1SPNJTF" W
   7
     (FOFSBUPS W
   7
     "TZOD
   'VODUJPOT
   BTZODBXBJU W
   7
     "TZOD
   *UFSBUJPO
   GPS
   BXBJUPG &YQFSJNFOUBM
5. BTZODBXBJUʹΑͬͯඇಉظॲཧͷϑϩʔ੍ޚ͸༰қʹͳ͕ͬͨɺ$BMMCBDLܕͷϝ ιου͸1SPNJTFʹม׵͠ͳ͚Ε͹ϑϩʔ੍ޚʹ૊ΈࠐΉ͜ͱ͕Ͱ͖ͳ͍ɻ1SPNJTF ʹରԠ͍ͯ͠ͳ͍ɺϑϩʔ੍ޚʹ૊Έࠐ·ΕΔͰ͋Ζ͏Ϟδϡʔϧ͸ҎԼͷ͍ͣΕ͔ͷ બ୒ΛഭΒΕͨɻ $BMMCBDLΛݱ୅తͳϑϩʔ੍ޚʹରԠͤ͞Δ  $BMMCBDLͷ··ܧଓ͢Δʢ1SPNJTFม׵͸ར༻ऀʹ೚ͤΔʣ
    1SPNJTFʹ੾Γସ͑ɺޓ׵ੑΛࣺͯΔ
    $BMMCBDLͱ1SPNJTFͷΠϯλʔϑΣʔεΛཱ྆ͤ͞Δ બ୒
6. $BMMCBDLͱ1SPNJTFͷΠϯλʔϑΣʔεΛཱ྆ͤ͞Δ  $BMMCBDLΛলུͨ࣌͠ʹ1SPNJTFΛฦ͢  1SPNJTFઐ༻ͷΠϯλʔϑΣʔεΛ௥Ճ͢Δ  ‣ 1SPNJTFܕͷϞδϡʔϧΛฦ͢  ‣ ϝιουνΣʔϯ͔Β1SPNJTFΛฦ͢  ‣ 4VGpY෇͖ͷؔ਺͔Β1SPNJTFΛฦ͢ Ϟδϡʔϧ಺Ͱ$BMMCBDLͱ1SPNJTFͷΠϯλʔϑΣʔεΛཱ྆ͤ͞Δํ๏ʹ͸͍ͭ͘ ͔ͷબ୒ࢶ͕͋ΓɺͦΕͧΕʹϝϦοτͱσϝϦοτ͕ଘࡏ͢Δɻ
7. $BMMCBDLͱ1SPNJTFͷཱ྆
   
   $BMMCBDLΛলུͨ࣌͠ʹ1SPNJTF͕ฦΔ // Callback func((data) => { console.log(data) }) // Promise const data = await func() console.log(data) ϚʔέοτΛௐࠪ͢ΔݶΓ͜ͷελΠϧͷ࠾༻ྫ͸ଟ͘ɺ+BWB4DSJQUͷจԽΛݟͯ΋ ύϥϝʔλΛলུͯ͠ڍಈ͕มΘΔ࢓૊Έ͸ଟ͘ଘࡏ͍ͯ͠Δɻ ϝιου͝ͱͷஈ֊తͳ1SPNJTFԽ͕ՄೳͰɺকདྷతͳ$BMMCBDLͷഇࢭ΋ࢹ໺ʹೖ Ε΍͍͢ɻͨͩ͠
   TFU5JNFPVU
   ΍
   DIJME@QSPDFTTFYFD
   ͷΑ͏ͳίʔϧόοΫؔ ਺Λड͚औΓɺಉ࣌ʹฦΓ஋΋ଘࡏ͢Δؔ਺ͱ͸૬ੑ͕ѱ͍ͨΊ஫ҙ͕ඞཁɻ
8. $BMMCBDLͱ1SPNJTFͷཱ྆
   
   1SPNJTFܕͷϞδϡʔϧΛฦ͢ // Callback const fs = require('fs') fs.readFile('/etc/hosts', (err, data) => { console.log(data) }) // Promise const fs = require('fs').promises const data = await fs.readFile('/etc/hosts') console.log(data) /PEFKTͷຊମ͕࠾༻͍ͯ͠Δํ๏ɻ͢΂ͯͷϝιουΛҰׅͰ1SPNJTFԽͰ͖Δͱ ͍͏ར఺͕͋Γɺ·ͨϞδϡʔϧͷ։ൃऀࢹ఺Ͱ͸طଘͷ$BMMCBDLؔ਺ʹखΛՃ͑Δ ඞཁ͕ͳ͍ͱ͍͏ར఺΋͋Δɻ ͔͠͠Ϟδϡʔϧ಺ʹଘࡏ͢Δ͢΂ͯͷཁૉΛෳ੡ͯ͠վम͢Δඞཁ͕͋ΔͨΊɺରԠ ͷίετ͸վम࣌ʹूத͢Δɻ
9. $BMMCBDLͱ1SPNJTFͷཱ྆
   
   ϝιουνΣʔϯ͔Β1SPNJTFΛฦ͢ // Callback func((data) => { console.log(data) }) // Promise const data = await func().promise() console.log(data) "84
   4%,
   GPS
   +BWB4DSJQU
   ͳͲ͕࠾༻͍ͯ͠Δํ๏ɻ1SPNJTFʹݶΒͣɺ4USFBN ͷΑ͏ͳෳ਺ύλʔϯͷΠϯλʔϑΣʔεΛ໌ࣔతʹࢦఆͯ͠ฦ͢͜ͱ΋Ͱ͖Δɻ طଘͷ$BMMCBDLؔ਺ʹखΛՃ͑Δඞཁ͕ͳ͍ͱ͍͏ར఺͕͋ΓɺϞδϡʔϧ಺ͷϝιο υΛ෦෼తʹ1SPNJTFରԠ͍ͯ͘͜͠ͱ΋Ͱ͖Δ͕ɺকདྷతͳ$BMMCBDLͷഇࢭΛࢹ ໺ʹೖΕΔ৔߹͸ѻ͍͕೉͍͠ɻ
10. $BMMCBDLͱ1SPNJTFͷཱ྆
    
    4VGpY෇͖ͷؔ਺͔Β1SPNJTFΛฦ͢ // Callback func((data) => { console.log(data) }) // Promise const data = await funcAsync() console.log(data) VUJMQSPNJTJGZ
    ΍
    CMVFCJSEQSPNJTJGZ"MM
    ͳͲΛར༻͢Δ͜ͱʹΑͬͯɺ࠷খݶ ͷίετͰϞδϡʔϧ಺ͷϝιουΛ1SPNJTFʹରԠ͢Δ͜ͱ͕Ͱ͖Δɻ কདྷతͳ$BMMCBDLͷഇࢭΛߟ͑Δ৔߹ɺޓ׵ੑʹͲ͏ରॲ͢Δ͔͕೰·͍͠ɻ4VGpYΛ ҡ࣋͢Δ͔ɺ·ͨ͸4VGpYΛআڈͯ͠1SPNJTFͷར༻ऀʹෛՙΛ༩͑Δ͔ͷબ୒͕ඞཁɻ
11. ֤ύλʔϯͷ۩ମతͳ࣮૷ํ๏͸ϒϩάͷهࣄ಺ʹɻ͓͢͢Ί͸ஈ֊తͳ1SPNJTFԽͱ $BMMCBDLͷഇࢭΛࢹ໺ʹೖΕ΍͍͢ʮ$BMMCBDLΛলུͨ࣌͠ʹ1SPNJTFΛฦ͢ʯํ๏ɻ $BMMCBDLͱ1SPNJTFͷΠϯλʔϑΣʔεΛཱ྆ͤ͞Δ  $BMMCBDLΛলུͨ࣌͠ʹ1SPNJTFΛฦ͢  1SPNJTFઐ༻ͷΠϯλʔϑΣʔεΛ௥Ճ͢Δ  ‣ 1SPNJTFܕͷϞδϡʔϧΛฦ͢  ‣ ϝιουνΣʔϯ͔Β1SPNJTFΛฦ͢  ‣ 4VGpY෇͖ͷؔ਺͔Β1SPNJTFΛฦ͢ ݸਓత͓͢͢Ί
12. ੑೳ
    ݱ୅తͳϑϩʔ੍ޚ͸ߴ଎ͳͷ͔ʁ
13. ݱ୅తͳϑϩʔ੍ޚ͸ߴ଎ͳͷ͔ʁ %PY#FFϕϯνʔϚʔΫͰ/PEFW؀ڥͷ$BMMCBDLͱ1SPNJTFɺBTZOD BXBJUͷύϑΥʔϚϯεΛܭଌ
    
    ‎
    
    ݱ࣌఺Ͱ͸$BMMCBDL͕࠷଎ εϧʔϓοτΛՄࢹԽ͍ͯ͠ΔͨΊ௿͚Ε͹௿͍ ΄ͲύϑΥʔϚϯε͕ߴ͍͜ͱΛද͢ɻ
    $BMMCBDL͸ଞͷඇಉظॲཧʹൺ΂ͯഒҎ্ͷύ ϑΥʔϚϯεΛୟ͖ग़͍ͯ͠Δɻແ৚݅ʹ͢΂ͯ ͷ$BMMCBDLΛ๾໓ͯ͠͸͍͚ͳ͍ɻ
    ϕϯνϚʔΫͷৄࡉ͸ԼهϦϙδτϦʹ
    IUUQTHJUIVCDPN"KJEPXIJDIJTUIF GBTUFTUBTZODQBUUFSO
14. BTZODBXBJU͸1SPNJTFΑΓ΋଎͘ͳΔ ࠷৽ͷ؀ڥͰ֤ඇಉظॲཧͷύϑΥʔϚϯεΛܭଌɻ7
    Ҏ্Ͱ͸BXBJUͷ࢓༷ม ߋΛ൐͏࠷దԽ͕ߦΘΕɺBTZODBXBJU͸1SPNJTFΑΓ΋ߴ଎ʹɻ /PEFWʹೖΔ͔΋ɻ
    Ϟδϡʔϧͷ಺෦Ͱ΋BTZODBXBJUΛར༻͠ ͯ1SPNJTFͷΠϯλʔϑΣʔεΛ࣮૷͢Δͱ͍ ͏ํ๏͕ΑΓ༗ޮʹͳΔɻ
    ͦͷ৔߹ɺࠓ೥݄ʹ&0-ͱͳΔ/PEFW؀ ڥΛߟྀ͢Δ͔Ͳ͏͔͕য఺ʹɻ
    IUUQTWEFWCMPHGBTUBTZOD
15. ݱ୅తͳϑϩʔ੍ޚ͸ߴ଎ͳͷ͔ʁ /PEFKTͷόʔδϣϯ͝ͱʹBTZODBXBJUͷύϑΥʔϚϯεΛܭଌ
    
    
    ‎
    
    BTZODBXBJU͸/PEFKTͷόʔδϣϯΞοϓʹ൐͍ܶతʹ଎౓͕޲্͍ͯ͠Δ ࠷దԽʹΑΓͦͷ଎౓͸$BMMCBDLʹഭΓ ͭͭ͋Δɻ
    1SPNJTFΑΓ΋BTZODBXBJUΛɻͦ͠ ͯBTZODBXBJUΛ׆༻͢ΔͳΒɺϥϯλ ΠϜͷϝδϟʔόʔδϣϯΞοϓ͸ੵۃత ʹߦͳ͍͖͍ͬͯͨɻ
16. ετϦʔϜରԠ
    4USFBNΛϑϩʔ੍ޚʹͲ͏૊ΈࠐΉʁ
17. 4USFBNͱϑϩʔ੍ޚ͸૬ੑ͕ѱ͍ ͜Ε·Ͱ4USFBNΛϑϩʔ੍ޚʹ૊ΈࠐΉ৔߹͸ɺ1SPNJTF ͰแΈࠐΈϫϯγϣοτͷΠϯλʔϑΣʔεʹม׵͢Δ͔ɺ ಠࣗʹΠςϨʔγϣϯରԠͤ͞Δͱ͍͏ঢ়گͩͬͨɻ const recv = new Promise((resolve, reject) => { let data = '' stream.on('data', (chunk) => { data += chunk }) stream.once('end', () => { return resolve(data) }) stream.once(‘error', (err) => { return reject(err) }) }) const data = await recv() const drain = (stream) => { return new Promise((resolve, reject) => { stream.once('data', (data) => { stream.pause() … resolve(data) }) stream.once('end', () => { … resolve(null) }) stream.once('error', (err) => { … reject(err) }) stream.resume() }) } const main = async () => { const stream = fs.createReadStream(‘file’) let data = null while (data = await drain(stream)) { console.log(data) } } 1SPNJTFͰแΈࠐΉ
    ϫϯγϣοτม׵ ෳࡶ೉ղͳ
    ΠςϨʔγϣϯରԠ
18. 4USFBNͷΤϥʔϋϯυϦϯά͸ಠಛ 4USFBNͷجఈΫϥεͰ͋Δ&WFOU&NJUUFSͷΤϥʔϋϯυϦϯά͸ಠಛͰ͋Γɺͦ ͷϋϯυϦϯά࿙Ε͸ϓϩηεͷΫϥογϡʹ௚݁͢Δɻಛʹ஫ҙ͕ඞཁͳઃܭύλʔ ϯͷͻͱͭɻ ઃܭύλʔϯ ΤϥʔϋϯυϦϯά Ϋϥογϡ ඇಉظॲཧ $BMMCBDL if (err) &WFOU&NJUUFS emitter.on(‘error') 1SPNJTF .catch() BTZODBXBJU try..catch
     .catch() ಉظॲཧ try..catch
    
    1SPNJTF
    
    BTZODBXBJU
19. "TZOD*UFSBUPSΛ࢖ͬͨ4USFBNͷϑϩʔ੍ޚ stream.on('data', (data) => { console.log(data) }) stream.on('end', () => { console.log('finished') }) stream.on(‘error', (err) => { console.error(err) }) try { for await (const data of stream) { console.log(data) } console.log(‘finished') } catch (err) { console.error(err) } 4USFBN "TZOD*UFSBUPS &4ͷػೳ
    "TZOD*UFSBUPS
    Λ׆༻͢Δ͜ͱͰɺ4USFBNΛγʔϜϨεʹϑϩʔ ੍ޚʹ૊ΈࠐΉ͜ͱ͕Ͱ͖ΔΑ͏ʹͳͬͨɻʢ&YQFSJNFOUBM
    "1*
    
    /PEFWʣ
20. "TZOD*UFSBUPSΛ࢖ͬͨ4USFBNͷϑϩʔ੍ޚ ςΩετϑΝΠϧΛߦ୯ҐͰॲཧͨ͠Γɺ)551ϦΫΤετͷDIVOLΛॲཧ͢Δ৔໘ͳ ͲͰ׆༻Ͱ͖Δɻ౷ҰతͳΤϥʔϋϯυϦϯά͕ඇৗʹັྗతɻ http.createServer(async (req, res) => { try { let body = '' req.setEncoding('utf8') for await (const chunk of req) { body += chunk } console.log(body) res.end() } catch { res.statusCode = 500 res.end() } }) const main = async () => { const rl = readline.createInterface({ input: fs.createReadStream('input.txt') }) for await (const line of rl) { console.log(line) } } main().catch((err) => { console.error(err) }) ࣍ʹ๾໓͞ΕΔͷ͸4USFBN͔ʁ
21. Τϥʔॲཧ
    ඇಉظॲཧͷελοΫτϨʔε͸Ͳ͏ݟ͑Δʁ
22. ඇಉظॲཧ๊͕͑ΔελοΫτϨʔεͷ՝୊ʢʣ ຊདྷελοΫτϨʔε͸σόοάͷॿ͚ʹͳΔ΋ͷ͕ͩɺඇಉظॲཧͷελοΫτϨʔ ε͸໾ʹཱͨͳ͍ɻඇಉظॲཧͷݺͼग़͠ݩ͸ɺඇಉظॲཧͷ։࢝Λ໋ྩͨ͠ίʔυͰ ͸ͳ͘ΠϕϯτϧʔϓͰ͋ΔͨΊɺಠཱͨ͠ελοΫτϨʔε͕දࣔ͞Εͯ͠·͏ɻ const exec = require('child_process').exec const func = (cb) => { exec('exit 1', (err) => { cb(err) }) } func((err) => { console.error(err) }) Error: Command failed: exit 1 at ChildProcess.exithandler at ChildProcess.emit at maybeClose at Socket.stream.socket.on at Socket.emit at Pipe._handle.close ࣮ߦ݁Ռ ݺͼग़͠ݩͷ
    GVOD
    ؚ͕·Ε͓ͯΒͣ
    ΤϥʔͷൃੜՕॴ͕ಛఆͰ͖ͳ͍
23. ඇಉظॲཧ๊͕͑ΔελοΫτϨʔεͷ՝୊ʢʣ "TZOD'VODUJPOͷ؀ڥԼͰ͸BXBJUʹΑͬͯελοΫτϨʔε͕෼཭͞ΕΔɻBXBJU Ͱதஅ͞Εͨؔ਺͸ϚΠΫϩλεΫΩϡʔ͔Βॲཧ͕࠶։͞ΕΔͨΊɺલड़ͷ໰୊ͱಉ ༷ʹؔ਺ͷݺͼग़͠ܦ࿏͕ҡ࣋͞Εͣɺ੾Γ཭͞Εͯ͠·͏ɻ const func = async () => { await 'interrupt' throw new Error('error') } const main = async () => { await func() } main().catch((err) => { console.error(err) }) Error: error at func at process._tickCallback at Function.Module.runMain at startup at bootstrapNodeJSCore ࣮ߦ݁Ռ ݺͼग़͠ݩͷ
    NBJO
    ؚ͕·Ε͓ͯΒͣ
    ΤϥʔͷൃੜՕॴ͕ಛఆͰ͖ͳ͍
24. ඇಉظॲཧ๊͕͑ΔελοΫτϨʔεͷ՝୊ʹରॲ͢Δ લड़ͨ͠ελοΫτϨʔεͷ՝୊͸ҎԼʹྻڍͨ͠ํ๏ʹΑͬͯରॲͰ͖Δɻ ํ๏ ֓ཁ JOTQFDUCSL
    
    $ISPNF
    %FW5PPMT w ༷ʑͳσόοάػೳΛ಺แ
    w Φʔόʔϔου͋Γʢߴίετʣ BTZOD@IPPLT
    
    USBDF
    
    DMBSJGZ w ߴ͍Մಡੑͱ࢖͍উखͷྑ͞
    w Φʔόʔϔου͋Γ BTZODTUBDLUSBDFT w Φʔόʔϔουͳ͠
    w BTZODBXBJUͷ՝୊ͷΈղܾՄೳ
25. ඇಉظॲཧ๊͕͑ΔελοΫτϨʔεͷ՝୊ʹରॲ͢Δ
    JOTQFDUCSL
    
    $ISPNF
    %FW5PPMT JOTQFDUCSL
    Φϓγϣ ϯ෇͖Ͱىಈɻ $ISPNF
    %FW5PPMT͔ Β֬ೝ͢Δɻ ελοΫτϨʔεʹ͸දࣔ͞Εͳ͍
    ܦ࿏΋දࣔ͞ΕΔ
26. ඇಉظॲཧ๊͕͑ΔελοΫτϨʔεͷ՝୊ʹରॲ͢Δ
    BTZOD@IPPLT
    
    USBDF
    
    DMBSJGZ USBDFϞδϡʔϧ͸ඪ४ϞδϡʔϧͷBTZOD@IPPLTΛར༻ͯ͠ɺඇಉظॲཧʹಠࣗίʔ υΛࠩ͠ࠐΈελοΫτϨʔεΛ֦ு͢ΔɻDMBSJGZϞδϡʔϧ͸ෆཁͳελοΫτϨʔ εΛআڈͯ͠ελοΫτϨʔεͷՄಡੑΛ޲্ͤ͞Δɻʢݸਓత͓͢͢Ίʣ ❯ node -r trace -r clarify exec.js Error: Command failed: exit 1 at func at Object.<anonymous> ࣮ߦ݁Ռ ݺͼग़͠ݩͷ
    GVOD
    ؚ͕·Ε
    ෆཁͳߦ΋࡟আ͞Ε͍ͯΔ const exec = require('child_process').exec const func = (cb) => { exec('exit 1', (err) => { cb(err) }) } func((err) => { console.error(err) })
27. ඇಉظॲཧ๊͕͑ΔελοΫτϨʔεͷ՝୊ʹରॲ͢Δ
    BTZODTUBDLUSBDFT 7
    Ҏ্ͷ؀ڥͰ͜ͷΦϓγϣϯΛ༗ޮʹ͢ΔͱɺBXBJUʹؚ·ΕΔ৘ใΛ࢖ͬͯ ඇಉظॲཧΛލ͍ͩελοΫτϨʔε͕ߏங͞ΕΔΑ͏ʹͳΔɻ෦෼తͳ໰୊ղܾखஈ Ͱ͸͋Δ͕ɺ࣮ߦதͷγεςϜʹෛՙΛ༩͑ͳֵ͍৽తͳػೳɻ const func = async () => { await 'interrupt' throw new Error('error') } const main = async () => { await func() } main().catch((err) => { console.error(err) }) ❯ node --async-stack-traces await.js Error: error at func at process._tickCallback at Function.Module.runMain at startup at bootstrapNodeJSCore at async main ࣮ߦ݁Ռ ݺͼग़͠ݩͷ
    NBJO
    ؚ͕·Ε͍ͯΔ ·ͩϑϥά෇͖ͷػೳɻࠓޙͷϑϥάղআʹظ଴
28. ϑϩʔ੍ޚͷ࠷దԽ͸$BMMCBDLΛ1SPNJTFʹม͚͑ͨͩͰ͸ ऴΘΒͳ͍ɻকདྷΛݟਾ͑ɺ͞ΒͳΔ࠷దԽΛਐΊΑ͏ʂ
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