NODE.JS SERVER SIDE JAVASCRIPT By Grégoire Charvet Slides on and github speaker deck 

ABOUT ME Full time node.js dev at Digbil Web dev for the past 2.5 years (front end and back end) 

NODE.JS: WHAT'S THAT? 

SERVER SIDE JAVASCRIPT 

IN DETAILS V8 javascript engine Node.js API replaces the DOM & browser API An event loop 

V8 ENGINE Controlled javascript env (es5) Some es6 features present in 0 . 1 1 (use - - h a r m o n y ) 

NODE.JS API Core api to access the file system, the network (http, sockets), crypto functions... No DOM More about the core api later 

EVENT LOOP Same as in the browsers. Event driven system New functions s e t I m m e d i a t e and p r o c e s s . n e x t T i c k Fundamental concept in node.js (watch: ) What the heck is the event loop anyway 

MODULE SYSTEM 

COMMONJS Synchronous r e q u i r e Expose API with m o d u l e . e x p o r t s 

EXPOSING STUFF In a file: a c t o r . j s f u n c t i o n A c t o r ( ) { t h i s . n a m e = ' B r a d P i t t ' } A c t o r . p r o t o t y p e . g e t N a m e = f u n c t i o n ( ) { r e t u r n t h i s . n a m e ; } m o d u l e . e x p o r t s . A c t o r = A c t o r ; 

GETTING STUFF FROM OTHER PLACES In a file: m a i n . j s v a r A c t o r = r e q u i r e ( ' . / a c t o r ' ) . A c t o r ; Synchronous call Relative path (. . / works too) . j s can be omitted 

EXTERNAL OR NATIVE MODULES Requiring an external module (see: p a c k a g e . j s o n later on) Will look up the module in n o d e _ m o d u l e s folder. v a r e x p r e s s = r e q u i r e ( ' e x p r e s s ' ) ; / / n o ` . / ` h e r e v a r c r y p t o = r e q u i r e ( ' c r y p t o ' ) ; / / n a t i v e n o d e . j s a p i 

SYNC VS ASYNC CALLBACK CONVENTION (CONTINUATION) 

A SYNCHRONOUS EXAMPLE Read a file / / n a t i v e n o d e m o d u l e t o a c c e s s t h e f i l e s y s t e m v a r f s = r e q u i r e ( ' f s ' ) ; t r y { v a r f i l e C o n t e n t = f s . r e a d F i l e S y n c ( ' . / m y F i l e . t x t ' ) ; } c a t c h ( e r r ) { c o n s o l e . l o g ( ' E r r o r w h i l e r e a d i n g f i l e : ' , e r r ) ; } ONE MAJOR CAVEAT Blocking code (and there is only one thread) 

USE ASYNC CODE IN NODE That's how it works Most api don't have synchronous equivalent 

HOW? v a r f s = r e q u i r e ( ' f s ' ) ; f s . r e a d F i l e ( ' . / m y F i l e . t x t ' , f u n c t i o n c a l l b a c k ( e r r , f i l e ) { i f ( e r r ) { c o n s o l e . l o g ( ' G o t a n e r r o r : ' , e r r ) ; } e l s e { c o n s o l e . l o g ( ' G o t f i l e h e r e ' ) ; } } ) ; 

ASYNC? v a r f s = r e q u i r e ( ' f s ' ) ; c o n s o l e . l o g ( ' a b o u t t o r e a d f i l e ' ) ; v a r r e s u l t = f s . r e a d F i l e ( ' . / m y F i l e . t x t ' , f u n c t i o n ( e r r , f i l e ) { i f ( e r r ) c o n s o l e . l o g ( ' e r r o r : ' , e r r ) ; e l s e c o n s o l e . l o g ( ' g o t f i l e ' ) ; } ) ; c o n s o l e . l o g ( ' d o n e r e a d i n g f i l e ? ' ) ; c o n s o l e . l o g ( ' r e s u l t : ' , r e s u l t ) ; Execution result: "about to read file" "done reading file" "result: undefined" "got file" (some time later) 

ERROR HANDLING t r y { s e t T i m e o u t ( f u n c t i o n ( ) { / / a n o t h e r a s y n c f u n c t i o n t h r o w n e w E r r o r ( ' c a t c h m e i f y o u c a n ' ) ; } , 0 ) ; } c a t c h ( e r r ) { c o n s o l e . l o g ( ' G o t y o u : ' , e r r ) ; } Result: * Error: catch me if you can at null._onTimeout (/home/greg/tests/error.js:2:9) at Timer.listOnTimeout (timers.js:133:15) (process crashed) 

CALLBACK CONVENTION f u n c t i o n c a l l b a c k ( e r r , a r g 1 , a r g 2 , a r g s . . . ) { / / e r r o r o b j e c t i s a l w a y s t h e f i r s t a r g u m e n t } d o S o m e t h i n g A s y n c ( ' f o o ' , ' b a r ' , ' b a z ' , c a l l b a c k ) ; / / t h e c a l l b a c k f u n c t i o n i s a l w a y s t h e l a s t a r g u m e n t All node.js ecosystem uses this convention 

IMPLICATIONS No return values Need to pass callbacks for async operations Don't throw error Uncaught errors will CRASH the whole program (process.on('uncaughtException', handler)); 

WHO CALLS MY CALLBACK??? The event loop is here for that 

INTERNALS v a r f s = r e q u i r e ( ' f s ' ) ; f s . r e a d F i l e ( ' . / m y F i l e . t x t ' , f u n c t i o n c a l l b a c k ( e r r , f i l e ) { i f ( e r r ) { c o n s o l e . l o g ( ' G o t a n e r r o r : ' , e r r ) ; } e l s e { c o n s o l e . l o g ( ' G o t f i l e h e r e ' ) ; } } ) ; Call the readFile function from node API And register the callback with readFile Do nothing in the main thread When readFile finishes, put the callback in the event loop If no js code is running at that point execute the callback (Otherwise, finish execution of code and execute first handler in the event loop) 

OTHER ASYNC CONSTRUCTIONS (ADVANCED) Promises (es6) Generators (es6) Async functions (es7) 

PACKAGE.JSON AND NPM { " n a m e " : " r e v e a l . j s " , " v e r s i o n " : " 2 . 6 . 2 " , " d e s c r i p t i o n " : " T h e H T M L P r e s e n t a t i o n F r a m e w o r k " , " h o m e p a g e " : " h t t p : / / l a b . h a k i m . s e / r e v e a l - j s " , " s u b d o m a i n " : " r e v e a l j s " , " s c r i p t s " : { " t e s t " : " g r u n t t e s t " , " s t a r t " : " " } , " a u t h o r " : { " n a m e " : " H a k i m E l H a t t a b " , " e m a i l " : " h a k i m . e l h a t t a b @ g m a i l . c o m " , " w e b " : " h t t p : / / h a k i m . s e " } , " r e p o s i t o r y " : { " t y p e " : " g i t " , " u r l " : " g i t : / / g i t h u b . c o m / h a k i m e l / r e v e a l . j s . g i t " } , " e n g i n e s " : { " n o d e " : " ~ 0 . 8 . 0 " } , " d e p e n d e n c i e s " : { " u n d e r s c o r e " : " ~ 1 . 5 . 1 " , " e x p r e s s " : " ~ 2 . 5 . 9 " , " m u s t a c h e " : " ~ 0 . 7 . 2 " , " s o c k e t . i o " : " ~ 0 . 9 . 1 3 " } , 

SIGNATURE OF NODE.JS PROJECTS 

GENERAL INFO { " n a m e " : " m y P a c k a g e N a m e " , " d e s c r i p t i o n " : " t h i s i s a v e r y u s e f u l d e s c r i p t i o n " , " h o m e p a g e " : " h t t p : / / f o o b a r . c o m " } 

VERSION { " v e r s i o n " : " 2 . 4 . 8 " } Uses s e m a n t i c v e r s i o n i n g 

SEMANTIC VERSIONING (SEMVER) Version follow the pattern x . y . z 

X.Y.Z Bugfix version Only minor changes and bug fixes x . y . z 1 and x . y . z 2 must be compatible Automatic upgrade 

X.Y.Z Minor version Can introduce new features Usually preserves backward compatibility Usually painless upgrades 

X.Y.Z Major version Reserved for breaking changes (new API) Should provide an upgrade guide 

REPO AND ENGINE { " r e p o s i t o r y " : { " t y p e " : " g i t " , " u r l " : " g i t : / / g i t h u b . c o m / h a k i m e l / r e v e a l . j s . g i t " } , " e n g i n e s " : { " n o d e " : " ~ 0 . 8 . 0 " } } 

LICENSE { " l i c e n s e s " : [ { " t y p e " : " M I T " , " u r l " : " h t t p s : / / g i t h u b . c o m / h a k i m e l / r e v e a l . j s / b l o b / m a s t e r / L I C E N S E " } ] } 

DEPENDENCIES { " d e p e n d e n c i e s " : { " u n d e r s c o r e " : " ~ 1 . 5 . 1 " , " e x p r e s s " : " ~ 2 . 5 . 9 " , " m u s t a c h e " : " ~ 0 . 7 . 2 " , " s o c k e t . i o " : " ~ 0 . 9 . 1 3 " } } Uses to parse Picked up by n p m i n s t a l l Installed under < r o o t D i r > / n o d e _ m o d u l e s / node semver 

MAIN { " m a i n " : " l i b / i n d e x . j s " } Entry point of your package 

SCRIPTS { " s c r i p t s " : { " t e s t " : " m o c h a - - b a i l t e s t / " , " s t a r t " : " n o d e l i b / s e r v e r . j s " , " p o s t i n s t a l l " : " n o d e n o d e _ m o d u l e s / . b i n / b o w e r i n s t a l l " } } Define script to be run with n p m r u n < s c r i p t n a m e > Some predefine scripts: n p m t e s t n p m s t a r t p o s t i n s t a l l automatically run after n p m i n s t a l l 

MORE d e v D e p e n d e n c i e s , p e e r D e p e n d e n c i e s c o n t r i b u t o r s Full doc 

NPM Stands for "Node Package Manager" Bundled with node Allow installation of dependency and compilation Some issues on windows dependency tree run too deep Sometimes native compilation is an issue 

WEB SERVERS 

Node is very strong for IO bound program. Native h t t p (and h t t p s ) module to create web servers. Very barebone api -> needs for some libraries/framework. Shines when there is a lot of quiet connections 

EXAMPLE OF A WEBSERVER A webserver in 11 lines. v a r h t t p = r e q u i r e ( ' h t t p ' ) ; f u n c t i o n r e q u e s t H a n d l e r ( r e q , r e s ) { r e s . s t a t u s C o d e = 2 0 0 ; r e s . e n d ( ' H e l l o ' ) ; } v a r s e r v e r = h t t p . c r e a t e S e r v e r ( r e q u e s t H a n d l e r ) ; v a r p o r t = 8 0 0 0 ; s e r v e r . l i s t e n ( p o r t , f u n c t i o n ( e r r ) { i f ( e r r ) c o n s o l e . e r r o r ( ' E r r o r w h e n s t a r t i n g s e r v e r : ' , e r r ) ; e l s e c o n s o l e . l o g ( ' S e r v e r s t a r t e d o n p o r t % d ' , p o r t ) ; } ) ; 

PITFALL Only one thread for your code: beware of processing time! f u n c t i o n f i b o ( n ) { r e t u r n n < 2 ? 1 : f i b o ( n - 1 ) + f i b o ( n - 2 ) ; } f u n c t i o n r e q u e s t H a n d l e r ( r e q , r e s ) { r e s . e n d ( S t r i n g ( f i b o ( 4 2 ) ) ) ; } a b - n 1 0 - c 1 0 h t t p : / / l o c a l h o s t : 8 0 0 0 / R e q u e s t s p e r s e c o n d : 0 . 2 8 [ # / s e c ] ( m e a n ) 

BARE BONE CORE API No routing (different handler for / f o o and / b a r ) No body parsing (stuff send with m u l t i p a r t - f o r m - d a t a or x - w w w - f o r m - u r l e n c o d e d No cookie support (need to parse them manually from the headers) 

WEB LIB/FRAMEWORK Express - by far the most popular one Restify - if you're only interested in API Koa - uses generators Kraken (paypal) Sails Loopback (see next talk) Waigo (koa based) 

THE MOST POPULAR ONE: EXPRESS v a r a p p = r e q u i r e ( ' e x p r e s s ' ) ( ) ; a p p . g e t ( ' / ' , f u n c t i o n ( r e q , r e s ) { r e s . s e n d ( ' H e l l o ' ) ; } ) ; a p p . g e t ( ' / p i n g ' , f u n c t i o n ( r e q , r e s ) { r e s . s e n d ( ' p o n g ' ) ; } ) ; a p p . g e t ( ' * ' , f u n c t i o n ( r e q , r e s ) { r e s . s t a t u s ( 4 0 4 ) . s e n d ( ' F o u r O h F o u r ' ) ; } ) ; a p p . l i s t e n ( 8 0 0 0 ) ; 

EXPRESS' MIDDLEWARES Handlers executed for each requests for a matching path Do some processing/logic Give back the control to the next handler 

TYPICAL EXPRESS APP v a r a p p = e x p r e s s ( ) ; a p p . u s e ( b o d y P a r s e r . u r l E n c o d e d ( ) ) ; a p p . u s e ( b o d y P a r s e r . j s o n ( ) ) ; a p p . u s e ( m u l t i p a r t ( ) ) ; a p p . u s e ( c o o k i e - p a r s e r ( ) ) ; a p p . u s e ( c o o k i e - s e s s i o n ( ) ) ; a p p . u s e ( c s u r f ( ) ) ; a p p . u s e ( c o m p r e s s i o n ( ) ) ; 

TYPICAL EXPRESS APP v a r a p p = e x p r e s s ( ) ; a p p . u s e ( b o d y P a r s e r . u r l E n c o d e d ( ) ) ; / / d e c o d e r e q u e s t ' s b o d y a p p . u s e ( b o d y P a r s e r . j s o n ( ) ) ; / / s a m e f o r j s o n a p p . u s e ( m u l t i p a r t ( ) ) ; a p p . u s e ( c o o k i e - p a r s e r ( ) ) ; a p p . u s e ( c o o k i e - s e s s i o n ( ) ) ; a p p . u s e ( c s u r f ( ) ) ; a p p . u s e ( c o m p r e s s i o n ( ) ) ; 

TYPICAL EXPRESS APP v a r a p p = e x p r e s s ( ) ; a p p . u s e ( b o d y P a r s e r . u r l E n c o d e d ( ) ) ; a p p . u s e ( b o d y P a r s e r . j s o n ( ) ) ; a p p . u s e ( m u l t i p a r t ( ) ) ; / / h a n d l e f i l e s a p p . u s e ( c o o k i e - p a r s e r ( ) ) ; a p p . u s e ( c o o k i e - s e s s i o n ( ) ) ; a p p . u s e ( c s u r f ( ) ) ; a p p . u s e ( c o m p r e s s i o n ( ) ) ; 

TYPICAL EXPRESS APP v a r a p p = e x p r e s s ( ) ; a p p . u s e ( b o d y P a r s e r . u r l E n c o d e d ( ) ) ; a p p . u s e ( b o d y P a r s e r . j s o n ( ) ) ; a p p . u s e ( m u l t i p a r t ( ) ) ; a p p . u s e ( c o o k i e - p a r s e r ( ) ) ; / / h a n d l e c o o k i e a p p . u s e ( c o o k i e - s e s s i o n ( ) ) ; / / s e s s i o n s a p p . u s e ( c s u r f ( ) ) ; a p p . u s e ( c o m p r e s s i o n ( ) ) ; 

TYPICAL EXPRESS APP v a r a p p = e x p r e s s ( ) ; a p p . u s e ( b o d y P a r s e r . u r l E n c o d e d ( ) ) ; a p p . u s e ( b o d y P a r s e r . j s o n ( ) ) ; a p p . u s e ( m u l t i p a r t ( ) ) ; a p p . u s e ( c o o k i e - p a r s e r ( ) ) ; a p p . u s e ( c o o k i e - s e s s i o n ( ) ) ; a p p . u s e ( c s u r f ( ) ) ; / / C S R F p r o t e c t i o n a p p . u s e ( c o m p r e s s i o n ( ) ) ; 

TYPICAL EXPRESS APP v a r a p p = e x p r e s s ( ) ; a p p . u s e ( b o d y P a r s e r . u r l E n c o d e d ( ) ) ; a p p . u s e ( b o d y P a r s e r . j s o n ( ) ) ; a p p . u s e ( m u l t i p a r t ( ) ) ; a p p . u s e ( c o o k i e - p a r s e r ( ) ) ; a p p . u s e ( c o o k i e - s e s s i o n ( ) ) ; a p p . u s e ( c s u r f ( ) ) ; a p p . u s e ( c o m p r e s s i o n ( ) ) ; / / g z i p c o m p r e s s i o n 

CLOSING THOUGHTS 

NODE.JS SPECIFIC APIS Buffers (b u f . r e a d U I n t 1 6 L E ), low level byte manipulation Streams, similar to unix steams (can be piped) Crypto (some system dependencies like openssl) Child processes and cluster File system, path & Os Net (low level networking, unix socket manipulation) 

ECOSYSTEM 

ECOSYSTEM All based on github, open sourced Write small modules, and compose them together One module should do one thing only, but well (unix philosophy) Virtually anything already exist 

CONSIDERATIONS WHEN USING NODE.JS Great for IO bound systems. Same language as the front-end: isomorphic application (meteor). One thread: suck to do any kind of processing. It's javascript: great for prototyping, requires rigor when growing. 

RESOURCES (video) Node.js docs npm & package.json 9 anti patterns for node.js teams Stream adventures 

WE'RE HIRING Interested to write node.js full time ? Production application Globally distributed (aws) Contact me: [email protected] 

Q&A