javascript - behind the scene

Slide 1

Slide 1 text

Javascript Behind the scene

Slide 2

Slide 2 text

Name !CSO 5BLFUPTIJ"POP੨໺݈ར Occupation 'SPOUFOE%FWFMPQFS1SPEVDU0XOFS Company $ZCFSBHFOU"EUFDI4UVEJP"*.FTTFOHFS OSS $POUSJCVUPSPG7 About IUUQJOGPCODI

Slide 3

Slide 3 text

ຊ೔࿩͢಺༰ ϒϥ΢β͸ͲͷΑ͏ʹJavascriptΛऔಘͯ͠ύʔε͢Δͷ͔ ͦͯ͠զʑ͸Ͳ͏࠷దԽ͢΂͖͔ʁ ͳΜͯݴ͍ͭͭ໨৽͍͜͠ͱ͸ແ͍Ͱ͢… ͋ͱ࣮ߦ࣌ͷ࿩͸࣌ؒͷؔ܎্͠·ͤΜ

Slide 4

Slide 4 text

Script Critical Path

Slide 5

Slide 5 text

Parse HTML Fetch Resources Parse and evaluate script

Slide 6

Slide 6 text

Parse HTML Fetch Resources Parse and evaluate script

Slide 7

Slide 7 text

Resource Fetching

Slide 8

Slide 8 text

Script Types Scriptʹ͸2ͭͷछྨͱ3ͭͷϑϥά͕͋Δɻ classic_script / module_script blocking / defer /async

Slide 9

Slide 9 text

Classic Script ͍ΘΏΔ௨ৗͷscriptλά ଟ͘ͷ৔߹͸ͪ͜ΒͷscriptΛ࢖͍ͬͯΔ͸ͣ

Slide 10

Slide 10 text

Module Script Ecmascript ModuleରԠͷscript type=moduleΛઃఆ͢Δ͜ͱͰಈ࡞͢Δ Import/exportͷॲཧΛμΠφϛοΫʹߦͬͯґଘͷղܾΛ͢Δ

Slide 11

Slide 11 text

Async scriptλάʹasyncϑϥάΛ෇༩͢Δ͜ͱͰscriptͷfetchλΠϛϯά ΛඇಉظՄ͢Δ͜ͱ͕Ͱ͖Δ ͦͷͨΊɺґଘ͋͠Θͳ͍scriptλά͸asyncͰ࣮ߦ͢Δ͜ͱ͕๬·͍͠

Slide 12

Slide 12 text

Defer scriptλάʹdeferϑϥάΛ෇༩͢Δ͜ͱͰscriptͷ࣮ߦλΠϛϯάΛ ඇಉظԽ͢Δ͜ͱ͕Ͱ͖Δ defer͸ඞͣscriptλάͷॱংͰ࣮ߦ͞ΕΔͨΊɺscriptͷॱংΛҡ࣋ ͭͭ͠script࣮ߦλΠϛϯάΛඇಉظʹ͍ͨ͠৔߹͸ͪ͜ΒΛ࢖͏

Slide 13

Slide 13 text

Behind the scene Connection

Slide 14

Slide 14 text

Create TCP Connection per resource ScriptϑΝΠϧͷϩʔυͷͨΊʹϒϥ΢β͸scriptλάͷsrc͔Βϩʔυ ͢΂͖ϦιʔεΛ୳͠ αʔό΁ϦΫΤετΛ౤͛Δ

Slide 15

Slide 15 text

Optimization

Slide 16

Slide 16 text

Limit of TCP Connection count per server HTTP1.1Λར༻͢Δ৔߹ɺࠓͷॴϒϥ΢β୯ҐͰಉ࣌઀ଓ੍ݶ͕ଘࡏ͢Δ ͦͷͨΊasync/deferଐੑΛར༻ͯ͠΋֎෦Ϧιʔε਺ͷ੍ݶʹҾ͔ͬ ͔ͬͨ৔߹ʹ͸଴͕ͪ࣌ؒൃੜ͢Δ

Slide 17

Slide 17 text

HTTP1.0 Connection limitation Queued

Slide 18

Slide 18 text

HTTP1.0 Connection limitation

Slide 19

Slide 19 text

TCP Connection limits for HTTP1.1 https://docs.pushtechnology.com/cloud/latest/manual/html/designguide/solution/support/connection_limitations.html

Slide 20

Slide 20 text

Using HTTP2.0 HTTP2.0Λར༻͢Δ৔߹ɺHTTP2.0ͷϦΫΤετɾϨεϙϯεଟॏԽʹ ΑͬͯυϝΠϯ୯ҐͰ1ͭͷίωΫγϣϯΛ࢖͍ճͨ͢Ί HTTP1.1ͷΑ͏ͳ઀ଓ਺੍ݶ͸ͳ͘ͳͬͨ(಺෦Ͱ͸͋Δ)

Slide 21

Slide 21 text

HTTP2.0 Multiplex connection

Slide 22

Slide 22 text

HTTP2.0 Multiplex connection " #

Slide 23

Slide 23 text

Behind the scene Fetching

Slide 24

Slide 24 text

Resource fetching ϒϥ΢β͸ϦιʔεΛ࣮ࡍʹऔಘ͢Δલʹ࣍ͷΑ͏ͳಈ࡞Λߦ͏

Slide 25

Slide 25 text

Browser resource fetching sequece Browser Cache 1. Check cache existence 2. Check cache expiration(if max-age specified) 3. Use cache or request updated resource If cache not stored, fetch resources Response with ETag: “…”, Cache-Control: “…” Gunzip if gziped Store cache if Cache-Control value isn’t “no-store”

Slide 26

Slide 26 text

Slide 27

Slide 27 text

Browser Cache ϒϥ΢βΩϟογϡΛར༻͢Δ͜ͱͰϦΫΤετݮগɾϨεϙϯεαΠζݮ গͷԸܙΛड͚Δ͜ͱ͕Ͱ͖Δ

Slide 28

Slide 28 text

ETag ϒϥ΢βΩϟογϡͷͨΊʹETagͱ͍͏࢓૊ΈΛ࢖͏ Cache-ControlͱETagͷ૊Έ߹ΘͤͰϦιʔεͷServerΛհͨ͠༗ޮͳΩϟογϡͷ࢓૊ΈΛ ར༻Ͱ͖Δ ϒϥ΢β͸ҎԼͷಈ࡞ΛͱΓ͏Δ - ϒϥ΢βΩϟογϡΛͦͷ··ར༻͢Δ - ϒϥ΢βΩϟογϡ͕ظݶ੾ΕͷͨΊɺϦΫΤετΛ౤͛ͯαʔό͔Β৽ͨͳϦιʔεΛऔಘ ͢Δ αʔό͸ҎԼͷબ୒ࢶ͕͋Δ - ETagϔομΛݟͯϦιʔε͕ߋ৽͞Ε͍ͯͳ͚Ε͹304 Not ModifiedͰϨεϙϯεແ͠ͷ ஋Λฦ͢ - ৽ͨͳϦιʔεͱETagΛฦ͢

Slide 29

Slide 29 text

ETag: “adda4f05-9bef-4a10-9f62-9ad11f3b9498” 3FTQPOTF If-None-Match: “adda4f05-9bef-4a10-9f62-9ad11f3b9498” 3FRVFTU

Slide 30

Slide 30 text

Browser resource fetching sequece #SPXTFS$BDIF $IFDLDBDIFFYJTUFODF $IFDLDBDIFFYQJSBUJPO JGNBYBHFTQFDJpFE 6TFDBDIFPSSFRVFTUVQEBUFESFTPVSDF *GDBDIFOPUTUPSFE GFUDISFTPVSDFT 3FTQPOTFXJUI&5BHlʜz $BDIF$POUSPMlʜz (VO[JQJGH[JQFE 4UPSFDBDIFJG$BDIF$POUSPMWBMVFJTO`UlOPTUPSFz

Slide 31

Slide 31 text

Cache-Control αʔό͸Cache-ControlϔομͰΫϥΠΞϯτʹରͯ͠ ΩϟογϡΛͲͷΑ͏ʹߦ͏͔ࢦࣔͰ͖Δ

Slide 32

Slide 32 text

Cache-Control: max-age=120 3FTQPOTF Cache-Control: s-maxage=120 Cache-Control: no-cache Cache-Control: no-store Cache-Control: immutable ϦΫΤετͷૹ৴ऀ͸௨ৗNBYBHFΛݟΔ͕ɺ $%/౳ͷ1SPYZαʔόͱΫϥΠΞϯτͰΩϟογϡ࣌ؒΛม͍͑ͨ৔߹ʹ͸ TNBYBHFͰ1SPYZଆͷNBYBHFͰΫϥΠΞϯτଆͷΩϟογϡ࣌ؒΛࢦఆ͢Δ͜ͱ͕Ͱ͖Δ OPDBDIFͷ৔߹͸DBDIFΛߦ͏͕ɺຖճαʔό΁ߋ৽ΛͨͣͶΔ OPTUPSFͷ৔߹͸DBDIFΛ׬શʹߦΘͳ͍ ·ͨJNNVUBCMFΛࢦఆ͢Δ͜ͱͰϖʔδϦϩʔυ࣌ͷ$POEJUJPOBM(&5 αʔό΁ͷߋ৽֬ೝ΋ఀࢭͰ͖Δ

Slide 33

Slide 33 text

Service Worker and Cache-Storage ServiceWorkerͰϦΫΤετΛinterruptͯ͠Ωϟογϡͨ͠ϦιʔεΛ ฦ͢͜ͱͰߋʹϦΫΤετ਺ΛݮΒ͢͜ͱ͕Ͱ͖Δ

Slide 34

Slide 34 text

ServiceWorker cache sequence $BDIF4UPSBHF $IFDLDBDIFFYJTUFODF *GDBDIFOPUTUPSFE GFUDISFTPVSDFT 3FRVFTUSFTPVSDF 4FSWJDF8PSLFS 4UPSFDBDIFUPTUPSBHF 3FHJTUFS4FSWJDF8PSLFS *OUFSSVQUSFRVFTUBOESFUVSOGSPN$BDIF4UPSBHF

Slide 35

Slide 35 text

Service Worker and Cache-Storage ೳಈతʹඞཁͳϦιʔεΛࣄલʹΩϟογϡ͢Δ͜ͱ͕Ͱ͖Δ ࣄલʹ಺༰͕ܾ·͍ͬͯΔ੩తίϯςϯπͷΩϟογϡʹ޲͍͍ͯΔ

Slide 36

Slide 36 text

Optimization

Slide 37

Slide 37 text

Preload link rel=preload Λ࢖͏͜ͱͰࣄલʹϒϥ΢βʹϦιʔεΛϩʔυ͓ͤͯ͘͞

Slide 38

Slide 38 text

Compress response ϨεϙϯεΛѹॖͯ͠ฦ٫͢Δ͜ͱͰɺϨεϙϯεαΠζΛখ͘͢͞Δ͜ͱ ͕Ͱ͖Fetching଎౓ʹେ͖͘Өڹ͢Δ ΞϧΰϦζϜͱͯ͠gzipͰ͸ͳ͘BrotliΛ࢖͏͜ͱͰߋʹѹॖ཰ΛߴΊΒ ΕΔ(ͨͩ͠ࣄલʹѹॖࡁΈϑΝΠϧΛ༻ҙ͢Δඞཁ͕͋Δ)

Slide 39

Slide 39 text

Caching 1. ETagΛઃఆ 2. Cache-ControlΛઃఆ 3. ServiceWorkerΛઃఆ ͜ͷ3εςοϓͰ Scriptͷߋ৽͕ͳ͚Ε͹1Ϣʔβʔʹରͯ͠1ϦΫΤετͷΈͷൃߦͰ ϦιʔεͷऔಘΛߦ͏͜ͱ͕Ͱ͖Δ

Slide 40

Slide 40 text

CDN CDN͔Β഑৴͢Δ͜ͱͰ ஍ཧతʹ͍ۙωοτϫʔΫ΁ΞΫηεͯ͠ɺFetching଎౓Λ޲্ͤ͞Δ CDNଆͰETagͱCache-ControlΛਖ਼͘͠ઃఆ͢Δ

Slide 41

Slide 41 text

Webpack Workbox΍sw-precacheͱ͍ͬͨpluginΛར༻͢Δ͜ͱͰ webpack͔ΒServiceWorkerͱΩϟογϡίʔυΛ؆୯ʹ࡞੒͢Δ͜ͱ͕ Ͱ͖Δ

Slide 42

Slide 42 text

Code Spliting ·ͨSPA౳͸࣮ࡍʹϑΝΠϧ͕ඞཁʹͳΔ·Ͱ FetchingΛ஗Ԇͤ͞Δ͜ͱͰແବͳϦΫΤετ΍ϖΠϩʔυͷαΠζΛݮ Β͢͜ͱ͕Ͱ͖Δ ྫ. React.Suspense + React.lazy + Dynamic Import + Webpack splitChunksͰϑΝΠϧ෼ׂ + ಈతಡΈࠐΈ

Slide 43

Slide 43 text

Future

Slide 44

Slide 44 text

HTTP/3 Quic HTTP৽όʔδϣϯͰ͋Γݱࡏࡦఆத Quicͷ্ʹߏங͞ΕΔHTTPϨΠϠ Quic͸TCPͰ͸ͳ͘UDP্ʹ᫔᫓੍ޚ౳Λ࣮૷ͨ͠Transport૚ͱͳͬͯ ͍Δ HTTP/3͸HTTP/2ͷར఺ΛҾ͖ܧ͗ͭͭɺTransport૚ࣗମͷվળʹΑͬ ͯߋʹߴ଎ͳϓϩτίϧͱͳΔ༧ఆ

Slide 45

Slide 45 text

Priority-hints WICGʹఏҊ͞Ε͍ͯΔ࢓༷ Resourceͷॏཁ౓Λώϯτͱͯ͠Τϯδϯʹ఻͑ΔͨΊͷimportanceଐ ੑ͕௥Ճ͞ΕΔ importanceଐੑʹ͸highɾlowɾautoͷͲΕ͔Λࢦఆ͢Δ͜ͱ͕Ͱ͖Δ

Slide 46

Slide 46 text

WebBundle/WebPackaging Web্ͷίϯςϯπΛ1ͭͷόϯυϧʹͯ͠഑৴͢ΔͨΊͷ࢓༷ WebαΠτؙ͝ͱPackagingͯ͠഑৴͢ΔͨΊʹ࢖͑Δ͕ɺScriptͷόϯ υϧΛ഑৴͢Δͷʹ΋࢖͑Δ͔΋ʁ

Slide 47

Slide 47 text

1BSTF)5.- 'FUDI3FTPVSDFT 1BSTFBOEFWBMVBUFTDSJQU

Slide 48

Slide 48 text

Parsing

Slide 49

Slide 49 text

Heavy but needed Parsingͱ͸Fetchͨ͠ScriptΛ࣮ߦ͢ΔͨΊʹίʔυΛParseͯ͠ Abstract Syntax Treeʹม׵͢ΔϑΣʔζ ͜ͷϑΣʔζΛܦͯScript͸Binary΁ม׵͞Ε࣮ߦ͞ΕΔ

Slide 50

Slide 50 text

if (x) { y = 100 }

Slide 51

Slide 51 text

Then Assign VarProxy Literal Expression Statement y = 100 100 y IF if Condition (x) Block {

Slide 52

Slide 52 text

Behind the scene Parsing

Slide 53

Slide 53 text

Large and Heavy ͨͩ͠ɺParseॲཧ͸ͱͯ΋ॏ͍ ಛʹ࠷ۙͷJS͸1όϯυϧʹͳ͓ͬͯΓ1ϑΝΠϧ୯ҐͷίʔυαΠζ΋େ ͖͍

Slide 54

Slide 54 text

Laziness Parse͸PreParseͱParseͷ2ͭͷϑΣʔζʹ෼͔ΕΔ javascript͸࣮ࡍʹ࣮ߦ͞ΕΔ·Ͱ࣮ߦ͞ΕΔίʔυ͕Θ͔Βͣɺ Parse࣌ؒ୹ॖͷͨΊʹॳճ͸ؔ਺໊ɾߦ൪߸ɾม਺৘ใͷΈΛύʔεͯ͠ ͓͖ɺ ݺͼग़͞ΕͨλΠϛϯάͰͦΕΒͷ৘ใΛ࢖࣮ͬͯࡍͷύʔεॲཧΛ͢Δ

Slide 55

Slide 55 text

function x(a, b) { return a + b; } Function(X) parameter-count: 2 start-position: 1 end-position: 1 use-super-property: false

Slide 56

Slide 56 text

// When x is called x() Return Function Name (x) BinaryExpression VarProxy a VarProxy b

Slide 57

Slide 57 text

Streaming Google ChromeͰ͸javascriptͰετϦʔϛϯάͰॲཧ͠ͳ͕ΒParse ͢Δ͜ͱͰɺFetchingͱParsingͷίετΛ཈͍͑ͯΔ

Slide 58

Slide 58 text

Stop parsing HTML javascriptͷParse͕࢝·ͬͨஈ֊ͰHTMLͷύʔεॲཧ͕ ఀࢭ͢ΔͨΊ scriptλάͷҐஔɾasyncɾdeferͷઃఆ͸ॏཁͱͳΔ

Slide 59

Slide 59 text

HTML Parsing and script execution flow Script HTML Script(defer) HTML Script(async) HTML Script(module) HTML Script(module, async) HTML HTML Parsing Script fetching Script execution

Slide 60

Slide 60 text

Optimization

Slide 61

Slide 61 text

Bundle size 50 ~ 100KB͋ͨΓΛ໨҆ʹίʔυͷ෼ׂΛߦͬͨ΄͏͕ྑ͍ ಛʹϞόΠϧσόΠεͰ͸Parsing࣌ͷCPUίετɾϝϞϦ࢖༻ྔ͕അࣛʹ ͳΒͳ͍

Slide 62

Slide 62 text

Async/Defer Chrome͸async/deferredͳscriptΛ·ͱΊͯίϯύΠϧ͢ΔͨΊɺ௨ ৗͷScriptΑΓ΋ߴ଎ʹॲཧͰ͖Δ ͨͩ͠asyncͰ͸࣮ߦΛ஗ԆͰ͖ͳ͍ͷͰɺͰ͖ΔݶΓscriptʹ͸defer ଐੑΛ෇༩ͨ͠΄͏͕ྑ͍

Slide 63

Slide 63 text

Transpiling Await/Generator͸Transpile͞ΕΔͱڊେͰඇޮ཰ͳίʔυΛੜ੒͢ ΔͨΊɺରԠϒϥ΢βʹ͸͜ΕΒ͕Transpile͞Ε͍ͯͳ͍όʔδϣϯΛ ఏڙ͢Δ΄͏͕๬·͍͠ instagramͰ͸transpileΛ΍ΊΔ͜ͱͰɺ5.7%ͷίʔυαΠζ࡟ݮ 3%ͷϩʔυ࣌ؒ࡟ݮΛ࣮ݱͨ͠ https://instagram-engineering.com/making-instagram-com-faster-code-size-and-execution-optimizations- part-4-57668be796a8

Slide 64

Slide 64 text

JSON.parse ΦϒδΣΫτϦςϥϧΛJSON.parse(“…”)ͷܗࣜͰهड़͢Δͱɺ࣮ߦ࣌· Ͱ׬શͳΦϒδΣΫτͷύʔεΛߦ͏λΠϛϯά͕ͣΕΔͨΊɺParsingͷ ύϑΥʔϚϯε͕޲্͢Δ ·ͨJSONΦϒδΣΫτʹ͸Getter/Setter౳͕ແ͍ͨΊɺParseࣗମ΋ ߴ଎ʹߦ͏͜ͱ͕Ͱ͖Δ

Slide 65

Slide 65 text

Immediate call V8Ͱ͸ଈ࣌ؔ਺ͷ৔߹ɺ஗ԆParseΛߦΘͳ͍ͷͰ ଈ࣮࣌ߦ͞ΕΔ΂͖ؔ਺͸ҎԼͷύλʔϯͰهड़͢ΔͱύϑΥʔϚϯε্͕ ͕Δ (function() {}) !function() {}() function() {}()

Slide 66

Slide 66 text

Polyfill Polyfill͸ϑΝΠϧαΠζΛ૿΍͠ɺParsingʹ͔͔Δ࣌ؒΛ૿΍͢ݪҼ ͱͳΓ͏Δ polyfill.ioΛར༻͢ΔͳͲͯ͠PolyfillͷαΠζ࡟ݮΛߦ͏΂͖ ·ͨɺຊདྷϖʔδશମͰ1ͭͷPolyfill͕๬·͍͕͠޿ࠂɾܭଌ౳ͷλά Λಋೖ͍ͯ͠Δ৔߹͸೉͍͔͠΋͠Εͳ͍͕…

Slide 67

Slide 67 text

Future

Slide 68

Slide 68 text

Binary AST ڞ௨ͷASTϑΥʔϚοτΛఆٛͯ͠ɺASTΛ௚઀഑৴͢Δ͜ͱͰɺParsing ͷίετΛ0ʹ͢Δ ݱࡏEcmascript΁proposal͕͋Δ͕ͦͷ͏ͪWhatwgʹҠಈ͢Δ༧ఆ

Slide 69

Slide 69 text

Appendix Execution

Slide 70

Slide 70 text

See https://speakerdeck.com/brn/source-to-binary-journey-of-v8-javascript- engine

Slide 71

Slide 71 text

͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠

Slide 72

Slide 72 text

Reference https://github.com/chromium/chromium https://v8.dev/blog/cost-of-javascript-2019 https://developers.google.com/web/fundamentals https://wicg.io/ https://instagram-engineering.com/making-instagram-com-faster-code-size-and- execution-optimizations-part-4-57668be796a8 https://html.spec.whatwg.org/multipage/scripting.html#attr-script-async https://blog.jxck.io/entries/2019-11-12/webbundle.html https://speakerdeck.com/brn/source-to-binary-journey-of-v8-javascript-engine