web performance part 4 "client-side performance"

Client-side performance

Mykyta Semenistyi

Table of contents

1. Perceived performance

2. Build systems

3. JavaScript

4. Data caching

5. CSS, rendering and fonts

6. DOM

7. Frameworks tweaking

8. Image optimizations

Perceived performance

0.1sfeels instantaneously

1smental context switch

10sinterest in dialog loss

JAKOB NIELSEN on January 1, 1993

Content loading

might not be loaded at once

Visual feedback

Icons by Seth Coelen http://dribbble.com/shots/1167728-PSD-CSS-Button-State-Workfiles

Instant Click

how long ago you gave yourself away

pjax-powered

Sleeping Devices

Page Visibility API hypnos

IE10+, FF 27+, Chrome 31+, iOS 7, Android 4.4, IEMobile 10, Safari 7+

visibilitychange event

hidden

Build systems

Grunt Gulp Broccoli

Build systemsOptimize images Generate sprites

Convert images Concatenate css, js,html

Minify css, js,html Inline css

Compress static files ...

JS performance

“Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at

efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time; premature optimization is the root of all evil. Yet we

should not pass up our opportunities in that critical 3%.”

Donald Knuth, Structured Programming With go to Statements

var person = { name: "Nicholas", age: 30};

function displayInfo(){ var count = 5; with(person){ alert(name + " is " + age); alert("Count is " + count); }}

displayInfo();

Execution context

Nicholas C. Zakas - Writing Efficient JavaScript: Chapter 7 - Even Faster Websites

for (var i = 0; i < theArray.length; i++) { copyOfTheArray[i] = theArray[i];}

var len = theArray.length;for (var i = 0; i < len; i++) { copyOfTheArray[i] = theArray[i];}

With caching:

Without caching:

Loops performance

for (var i in theArray) { copyOfTheArray[i] = theArray[i];}

theArray.forEach(function(it, idx){ copyOfTheArray[idx] = it;});

forEach:

for in:

Loops performance

WebWorkersBring threading to JS

UI Thread:

var worker = new Worker('task.js');worker.addEventListener('message', function(e) { console.log('Worker said: ', e.data);}, false);

worker.postMessage('Hello World');worker.terminate();

Worker:

self.addEventListener('message', function(e) { //e.data === ‘Hello World’; //process data self.postMessage(result);}, false);self.close();

var blob = new Blob([ "onmessage = function(e) { postMessage('msg from worker'); }"]);

// Obtain a blob URL reference to our workervar blobURL = window.URL.createObjectURL(blob);

var worker = new Worker(blobURL);

On fly:

Eric Bidelman http://www.html5rocks.com/en/tutorials/workers/basics/

WebWorkersPeculiarities

Dedicated Sharedavailable within the

creator scriptavailable within the same

domain scriptsWorkers have access to:

● The navigator object● The location object (read-only)● XMLHttpRequest● setTimeout etc.● The Application Cache● Importing external scripts using the importScripts() method● Spawning other web workers

Workers do NOT have access to:

● The DOM (it's not thread-safe)● The window object● The document object● The parent object

Transferrable types:● string● JSON● binary data (File, Blob, ArrayBuffer)

WebWorkersUse cases

Ray TracerVideo/audio

Route Tracer

DNA Analyzing

WebWorkersbut...

Event loop in JSUI Thread

...onclick XHR state change

setTimeout setInterval

onclick XHR state change

setTimeout

Long running scripts

var sum = 0;for (var i = 0; i < 23000000; i++){

sum += Math.random() * i;}

chunks

by count

by time

if (Date.now() - start > 100){ setTimeout(process);} else { process();}

if (i % 10000 === 0){ setTimeout(process);} else { process();}

asm.js“use asm”;

JIT vs AOT

no need for dynamic type guards, boxed values, and garbage collection.

asm.jswat...

asm.jshow to write

function strlen(ptr) { ptr = ptr|0; var curr = 0; curr = ptr; while (MEM8[curr]|0 != 0) { curr = (curr + 1)|0; } return (curr - ptr)|0; }

asm.jswhy

Native code

NaCl PNaClexecutes native code securely

through Software Fault Isolation (SFI)

1. compiling the source code to a portable bitcode format

2. translating the bitcode to a host-specific executable.

Data caching

Caching is tricky. Avoid it to reduce complexity, allowing you to focus on what matters: javascript variable

minification.@webperftips

1. someFunction(‘param’); 2. someFunction(‘param’);

results[‘param’] = result;

result

return result;

return results[‘param’];

Memoize

Util libraries: Standalone modules:

Memoize.js

Memoize

localStorage sessionStorage

Web Storage

clears when window is closed+:

1. IE8+

2. Simple API

3. Simple sync API

-:

1. Poor performance for large data

2. Lack of indexing

3. Manual serialization

Michael Mahemoff http://www.html5rocks.com/en/tutorials/offline/storage/

if (!localStorage.checkins) localStorage.checkins = JSON.stringify([]);

Web Storage

basket.require( { url: 'jquery.js' }, { url: 'underscore.js' }, { url: 'backbone.js' });

IndexedDB

Michael Mahemoff http://www.html5rocks.com/en/tutorials/offline/storage/

+:

1. Good performance

2. Async API

3. Search is indexed

4. Transactions

-:

1. IE10+

2. Complex API

var request = indexedDB.open("geomood", version);request.onupgradeneeded = function(event) {}request.onsuccess = function(event) {}

IndexedDB

WebSQL

+:

1. Mobile support

2. Good performance

3. Async API

4. Search is indexed

5. Transactions

-:

1. Deprecated (IE and FF)

2. Requires knowledge of SQL

3. SQL

Michael Mahemoff http://www.html5rocks.com/en/tutorials/offline/storage/

WebSQL

Michael Mahemoff http://www.html5rocks.com/en/tutorials/offline/storage/

this.db = openDatabase('geomood', '1.0', 'Geo-Mood Checkins', 8192);

this.db.transaction(function(tx) { tx.executeSql("create table if not exists " + "checkins(id integer primary key asc, time integer, latitude float," + "longitude float, mood string)", [],

function() { console.log("success"); } );});

WebSQL

localForage

WebSQL IndexedDB

localStorage-like API

localforage.setItem('key', 'value', doSomethingElse);

CSS, fonts, rendering

Larger font sizes cost significantly more across the wire. For quick web font loading, keep them under 10pt.

@webperftips

CSS Frameworks

~98 kB ~146 kB

~ 90% of the CSS rules are unused

grunt-uncss

CSS selectors

Ben Frain http://benfrain.com/css-performance-revisited-selectors-bloat-expensive-styles/

1. Data attribute2. Data attribute (qualified)3. Data attribute (unqualified but with value)4. Data attribute (qualified with value)5. Multiple data attributes (qualified with values)6. Solo pseudo selector (e.g. :after)7. Combined classes (e.g. class1.class2)8. Multiple classes9. Multiple classes with child selector

10. Partial attribute matching (e.g. [class^=“wrap”])11. nth-child selector12. nth-child selector followed by another nth-child

selector13. Insanity selection (all selections qualified, every class

used e.g. div.wrapper > div.tagDiv > div.tagDiv.layer2 > ul.tagUL > li.tagLi > b.tagB > a.TagA.link)

14. Slight insanity selection (e.g. .tagLi .tagB a.TagA.link)15. Universal selector16. Element single17. Element double18. Element treble19. Element treble with pseudo20. Single class

Test Chrome 34 Firefox 29 Opera 19 IE9 Android 4

1 56.8 125.4 63.6 152.6 1455.2

2 55.4 128.4 61.4 141 1404.6

3 55 125.6 61.8 152.4 1363.4

4 54.8 129 63.2 147.4 1421.2

5 55.4 124.4 63.2 147.4 1411.2

6 60.6 138 58.4 162 1500.4

7 51.2 126.6 56.8 147.8 1453.8

8 48.8 127.4 56.2 150.2 1398.8

... ... ... ... ... ...Biggest Diff. 16 13.6 17.6 31 152

Slowest 13 6 13 10 6

Dynamic CSS● dynamic properties

● media-queries

● key-frames animations

veinjs

vein.inject([{ '@media (max-width: 768px)': ['h2']}], { 'color': '#f00'});

vein.inject( ['h2', 'h3'], {'color' : 'green', 'font-weight' : null});

Dynamic CSSwhy

Layout performance

this block is being repainted on each

css change

Layout performancelayers

● -webkit-transform: translateZ(0)

● -webkit-transform: translate3d

(0,0,0);

● backface-visibility: hidden

GPU Acceleration

New Layer

● not enough VRAM

● slow CPU to GPU transfer

Layout performancelayers

Pitfalls:

Reflowgeometrical calculations of layout

el:clientHeightclientLeftfocus()getBoundingClientRect()getClientRects()innerTextoffsetHeightoffsetWidthouterTextscrollTopscrollWidth

window:getComputedStyle()scrollBy()scrollTo()scrollXscrollYwebkitConvertPointFromNodeToPage()webkitConvertPointFromPageToNode()

Layout performancesummary

● Try to localize changes● Try to batch changes FastDOM

● window.requestAnimationFrame

● disable animations when possible

● don’t cause reflow

Fonts loadtime1. Load only fonts you need

2. Load only charsets you need

3. Font Load Events API

Ilya Grigorik http://www.igvita.com/2014/01/31/optimizing-web-font-rendering-performance/

var font = new FontFace("FontA", "url(http://mysite.com/fonts/fontA.woff)", {});

font.ready().then(function() { // font loaded.. swap in the text / define own behavior.});

font.load(); // initiate immediate fetch / don't block on render tree!

DOM

Inserting <br> elements liberally throughout your markup will give the rendering engine enough breaks to stay fast for the

whole day.@webperftips

<!doctype html><html lang="en"><head>

...<link rel="stylesheet" href="">

</head><body>

... <script type=“text/javascript” src=""></script></body></html>

in the head to get styling asap

in the bottom of the bodynon-blocking

asyncdefer

Document parsing

Text editing

innerHTML innerText textContenthtml parsing layout reflow bingo! IE9+

Frameworks

Instead of doing costly ajax calls to a server for data, simply generate random data on the client side

and use that instead.@webperftips

you might not need jQueryIE8+

$(‘selector’) document.querySelectorAll(‘selector’)$.ajax new XMLHttpRequest().animate() CSS3 Animations.addClass() .classList.add().html() .innerHTML

...

jQuery-free frameworks

React vue.js

MVVMultra-fast

~13 kb gzipped

widget-orientedfastvirtualDOM

Backbone

grunt-contrib-jstJquery-less

document.fragment

Image optimizations

Sprites

Icons by Denis http://www.iconarchive.com/show/cat-commerce-icons-by-iconka.html

add.png client.png mail.png search.png trash.png

sprite.png

Sprites

.sprite-add-icon { background-position: 0 0; width: 128px; height: 128px; } .sprite-client-icon { background-position: -178px 0; width: 128px; height: 128px; }

.sprite-mail-icon { background-position: -356px 0; width: 128px; height: 128px; }

.sprite-search-icon { background-position: -534px 0; width: 128px; height: 128px; }

.sprite-trash-icon { background-position: -712px 0; width: 128px; height: 128px; }

css snippets

Inline images<img src="data:image/jpg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD/2w………….. />

background-image: url('data:image/jpg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD/2wBDAAcF……..’)

+:1. One request2. IE7+

-:1. base64 > image size2. not cached itself3. processor time

Inline images

Peter McLachlan http://www.mobify.com/blog/base64-does-not-impact-data-uri-performance/

Inline images vs sprites

Peter McLachlan http://www.mobify.com/blog/css-sprites-vs-data-uris-which-is-faster-on-mobile/

Serving perfect sized images1. Scaling the size down with css (e.g. 50%) 2. Serving bad/small images on Retina

problem

Serving perfect sized imagessolutions

media-queries srcset

( (min-device-pixel-ratio: 1.5) and (min-width: 20.001em) and (max-width: 35.999em) ) or( (max-device-pixel-ratio: 1.5) and (min-width: 120.001em) ) or( (min-device-pixel-ratio: 1.5) and (min-width: 60.001em) )

IE9+, FF 23+, Chrome 31+, iOS 3.2, Android 2.1, IEMobile 10, Safari 7+

<img src="small.jpg" srcset="large.jpg 1024w,

medium.jpg 640w, small.jpg 320w"sizes="(min-width: 36)33.3%, 100%"

/>

Chrome 33+, FF 27+, Safari 7+

Font icons

Font iconsicnfnt Fontello IcoMoon

custom builds

Compression

lossy lossless

strip metadatagroup

color quantization

OptiPNG

pngquant

jpegtrangifsicle

New, optimized formats

➔ webp25% less sizeChrome 9+ (stable 23+), Opera 12.1+, Android 4.0+

➔ jpeg-xr... less sizeIE9+

➔ mozjpegwork in progressjpeg compressor

New, optimized formats

Nicholas Doyle http://calendar.perfplanet.com/2013/browser-specific-image-formats/

Convertion tools

Probably the most universal tool. Any kind of convertion, lossless and lossy compression

webp cross-platform codec

ImageMagick

webpjpegxr cross-platform codecbmp -> jpegxr

jxrlib

Conditional serving

webp-detect

connect-image-optimus

koa-image-optimus

apachenginxvarnish

iisAccepts webp

webp on disk

1

add Vary:Accept

1

UA accepts jpegxr

jpegxr on disk

1

0