Frontend performance - where it matters

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FRONTEND PERFORMANCE WHERE IT MATTERS Frontend Conference 2013 Urban Etter

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ABOUT ME

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URBAN LEGENDS

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URBAN MYTHS

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URBAN ETTER

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SCHWEIZER RADIO UND FERNSEHEN

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ARCHITECT

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PART OF THE FRONTEND TEAM

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@URBMC

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PERFORMANCE IS A HUGE TOPIC

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CACHE INVALIDATION

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VERTICAL SCALING

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DATABASE CLUSTERS

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THIS TALK IS NOT ABOUT THAT

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ADVICES FOR CREATING SINGLE-PAGE WEB APPS

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[ ' h e l l o ' , ' w o r l d ' ] . j o i n ( ' ' ) instead of ' h e l l o ' + ' ' + ' w o r l d '

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THIS TALK IS NOT ABOUT THAT EITHER

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GOOD PRACTICE

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SOME TRAPS

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SOME CODE

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FRONTEND PERFORMANCE FOR THE CRAFTSMAN

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#1 PERFORMANCE MATTERS #2 LOADING PROCESS #3 DON'T BLOCK THE BROWSER #4 DEFERRED LOADING OF JS

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#5 BROWSER CACHE #6 TOOLS #7 DOM MANIPULATION #8 RECAP

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#1 PERFORMANCE MATTERS

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... that slowing down the search results page by 100 to 400 milliseconds has a measurable impact on the number of searches per user of -0.2% to -0.6% by Google

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To get that sensation, your requests need to take less than 100ms. by 37 signals

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PERFORMANCE IS A FEATURE

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IT TAKES EFFORT TO GET IT RIGHT

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IT CONFLICTS WITH OTHER FEATURES REDUCED COMPLEXITY MAINTAINABILITY SECURITY

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COMPLEX

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INVOLVES EVERY DISCIPLINE IN WEB DEVELOPMENT

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#2 LOADING PROCESS

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KEY TO FRONTEND PERFORMANCE IS TO UNDERSTAND THE PAGE LOADING PROCESS

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A LOT FASTER A LOT MORE FILES

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TIMING POINT #1: FETCH THE INITIAL HTML TIMING POINT #2: REACH DOM READY TIMING POINT #3: REACH "LOADED" EVENT

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NOT ALL IMAGES LOAD IN PARALLEL

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RESTRICTION IS PART OF THE HTTP STANDARD

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2 PARALLEL CONNECTIONS PER HOST for older browsers

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MODERN BROWSERS 6 PARALLEL CONNECTIONS PER HOST

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#3 DON'T BLOCK THE BROWSER

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< h e a d > < l i n k r e l = " s t y l e s h e e t " h r e f = " s t y l e . c s s " > < s c r i p t s r c = " s c r i p t . j s " > < / s c r i p t > < / h e a d > M y f a n c y c o n t e n t

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JS LOADING AND PARSING BLOCKS THE RENDERING PROCESS

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SOLUTION 1

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USE THE A S Y N C ATTRIBUTE

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< h e a d > < l i n k r e l = " s t y l e s h e e t " h r e f = " s t y l e . c s s " > < s c r i p t s r c = " s c r i p t . j s " a s y n c > < / s c r i p t > < / h e a d > M y f a n c y c o n t e n t

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A S Y N C == NOT BLOCKING

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SOLUTION 2 Preferred

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PUT JS AT THE END OF THE BODY TAG

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< h e a d > < l i n k r e l = " s t y l e s h e e t " h r e f = " s t y l e . c s s " > < / h e a d > M y f a n c y c o n t e n t < s c r i p t s r c = " s c r i p t . j s " > < / s c r i p t >

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#4 DEFERRED LOADING OF JAVASCRIPT

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NOT ALL JS IS NEEDED IN ALL SITUATIONS

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LOAD CALENDAR JS WHEN CLICKING ON THE CALENDAR

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LOAD CALENDAR JS WHEN HOVERING OVER THE CALENDAR

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PROBLEM: DELAY ON HOVERING

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LOAD CALENDAR JS WHEN ALL OTHER CODE IS LOADED

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RESULT: ADDED COMPLEXITY

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PERFORMANCE IS A FEATURE

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NOT WORTH IT UNLESS YOU ARE CREATING A SINGLE-PAGE APPLICATION

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BEEN THERE, DONE THAT

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DEFERRED != BAD

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DEFERRED IMAGE LOADING FTW

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LAZY LOAD JQUERY PLUGIN Lazy load plugin for jQuery

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#5 BROWSER CACHE

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THE GOOD AND THE BAD PARTS

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ALL JS IN ONE FILE TELL THE BROWSER TO CACHE IT BROWSER ONLY HAS TO DOWNLOAD IT ONCE

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FREE FOR THE REST OF THE STAY

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BETTER HAVE ONE BIG REQUEST

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THAN HAVE A LOT OF SMALL REQUESTS

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CSS SPRITES

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. s p r i t e - m u s i k w e l l e { b a c k g r o u n d - p o s i t i o n : 0 0 ; . s p r i t e - s r f 1 { b a c k g r o u n d - p o s i t i o n : - 6 6 p x 0 ; w i . s p r i t e - s r f 2 { b a c k g r o u n d - p o s i t i o n : - 1 3 2 p x 0 ; w . s p r i t e - s r f 3 { b a c k g r o u n d - p o s i t i o n : - 1 9 8 p x 0 ; w . s p r i t e - s r f 4 { b a c k g r o u n d - p o s i t i o n : - 2 6 4 p x 0 ; w . s p r i t e - v i r u s { b a c k g r o u n d - p o s i t i o n : - 3 3 0 p x 0 ;

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PERFORMANCE IS A FEATURE

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COMPLEXITY VS PERFORMANCE

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THE BAD PARTS

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YOU CHANGE YOUR CSS

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BROWSER CACHED CSS

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< s c r i p t s r c = " s c r i p t . j s " > < / s c r i p t >

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< s c r i p t s r c = " s c r i p t . j s ? v = 1 2 " > < / s c r i p t >

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< h e a d > < l i n k r e l = " s t y l e s h e e t " h r e f = " s t y l e . c s s " > < / h e a d > M y f a n c y c o n t e n t { r e n d e r _ i n c l u d e ( ' g l o b a l ' ) }

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[ g l o b a l ] j a v a s c r i p t [ ] = j q u e r y . j s j a v a s c r i p t [ ] = j q u e r y . c o o k i e . j s . . .

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f u n c t i o n r e n d e r _ i n c l u d e ( g r o u p N a m e ) { f i l e s = g e t F i l e s B y G r o u p ( g r o u p N a m e ) ; i f ( f i l e s . n e w e s t > l a s t R u n . t i m e s t a m p ) { r e s u l t = p a c k ( c o n c a t e n a t e ( f i l e s ) ) ; f i l e n a m e = m d 5 ( f i l e s . n e w e s t ) ; s a v e _ f i l e ( f i l e n a m e , r e s u l t ) ; } e l s e { f i l e n a m e = l a s t R u n . f i l e n a m e ; } r e t u r n ' < s c r i p t s r c = " f i l e n a m e " > ' ; }

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#6 TOOLS

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YSLOW

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CHROME DEVELOPER TOOLS

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GOOGLE PAGESPEED INSIGHTS

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WEB PAGE TEST

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REGRESSION TEST

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SHOW SLOW

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#7 DOM MANIPULATION

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DOM INTERNAL HTML REPRESENTATION ACCESSIBLE BY JS

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$ ( ' # m s g ' ) . a d d C l a s s ( ' v e r y _ i m p o r t a n t ' ) ; LOOK UP THE ELEMENT WITH ID "MSG" IN THE INTERNAL STRUCTURE MODIFY THE INTERNAL STRUCTURE RERENDER (AT LEAST PARTS) OF THE PAGE

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SAVE DOM MANIPULATIONS

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REAL WORLD EXAMPLE

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FILTERING

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COLUMN MARKUP IN 2

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HTML - SELECTS < s e l e c t i d = " t o p i c " > < o p t i o n v a l u e = " t o p i c : n e w s " > N e w s < / o p t i o n > < o p t i o n v a l u e = " t o p i c : t w i t t e r - r e l e v a n t " > T w i t t e r r e l e v a n t < / o p t i o n > < / s e l e c t >

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HTML - LETTERS < d i v c l a s s = " l e t t e r " d a t a - l e t t e r = " t " > < l i d a t a - a t t r = " t o p i c : n e w s , s t a t i o n : s r f 1 " > T a g e s s c h a u < / l i > < l i d a t a - a t t r = " t o p i c : t w i t t e r - r e l e v a n t " > T a t o r t < / l i > < / d i v >

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FIRST APROACH v a r t o p i c = $ ( ' # t o p i c - f i l t e r ' ) . v a l ( ) ; v a r s t a t i o n = $ ( ' # s t a t i o n - f i l t e r ' ) . v a l ( ) ; v a r s e l e c t o r = ' [ d a t a - a t t r * = " ' + t o p i c + ' " ] ' + ' [ d a t a - a t t r * = " ' + s t a t i o n + ' " ] ' ; $ ( ' l i ' ) . s h o w ( ) ; / / r e s e t $ ( ' l i : n o t ( ' + s e l e c t o r + ' ) ' ) . h i d e ( ) ;

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RESULT

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SECOND APPROACH HIDE ALL SHOWS ITERATE THROUGH LETTERS CLONE MATCHING SHOWS APPEND CLONED SHOWS TO LEFT OR RIGHT LIST SHOW CLONED SHOWS

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ITERATING AND CLONING $ ( ' d i v . l e t t e r ' ) . e a c h ( f u n c t i o n ( ) { $ ( ' l i . s h o w ' ) . h i d e ( ) . f i n d ( s e l e c t o r ) . c l o n e ( ) . a d d C l a s s ( ' c o p i e d ' ) . a p p e n d T o ( ' b o d y ' ) ; . . . } ) ;

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ITERATING AND CLONING . . . $ ( ' l i . c o p i e d ) . e a c h ( f u n c t i o n ( ) { / / a p p e n d t o l e f t o r r i g h t u l $ ( t h i s ) . s h o w ( ) ; } ) ; . . .

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THIS WAS SLOW

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THIRD APPROACH

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ITERATING $ r e p o s i t o r y = $ ( ' l i . s h o w ' ) . h i d e ( ) ; $ ( ' d i v . l e t t e r ' ) . e a c h ( f u n c t i o n ( ) { $ r e p o s i t o r y . f i n d ( s e l e c t o r ) . c l o n e ( ) . e a c h ( f u n c t i o n ( ) { / / a p p e n d t o l e f t o r r i g h t u l } ) . s h o w ( ) ; } ) ;