Even Faster Web Sites covering splitting the initial payload, loading scripts without blocking, and coupling asynchronous scripts.

2. the importance of frontend performance 17% 83% iGoogle, primed cache 9% 91% iGoogle, empty cache

3. time spent on the frontend April 2008 Empty Cache Primed Cache www.aol.com 97% 97% www.ebay.com 95% 81% www.facebook.com 95% 81% www.google.com/search 47% 0% search.live.com/results 67% 0% www.msn.com 98% 94% www.myspace.com 98% 98% en.wikipedia.org/wiki 94% 91% www.yahoo.com 97% 96% www.youtube.com 98% 97%

4. the performance golden rule 80-90% of the end-user response time is spent on the frontend. Start there. greater potential for improvement simpler proven to work

11. Even Faster Web Sites Splitting the initial payload Loading scripts without blocking Coupling asynchronous scripts Positioning inline scripts Sharding dominant domains Flushing the document early Using iframes sparingly Simplifying CSS Selectors Understanding Ajax performance.......... Doug Crockford Creating responsive web apps............ Ben Galbraith, Dion Almaer Writing efficient JavaScript............. Nicholas Zakas Scaling with Comet..................... Dylan Schiemann Going beyond gzipping............... Tony Gentilcore Optimizing images................... Stoyan Stefanov, Nicole Sullivan

12. Why focus on JavaScript? AOL eBay Facebook MySpace Wikipedia Yahoo! YouTube

13. scripts block <script src=&quot;A.js&quot;> blocks parallel downloads and rendering 7 secs: IE 8, FF 3.5, Chr 2, Saf 4 9 secs: IE 6-7, FF 3.0, Chr 1, Op 9-10, Saf 3

14. initial payload and execution 26% avg 252K avg JavaScript Functions Executed before onload www.aol.com 115K 30% www.ebay.com 183K 44% www.facebook.com 1088K 9% www.google.com/search 15K 45% search.live.com/results 17K 24% www.msn.com 131K 31% www.myspace.com 297K 18% en.wikipedia.org/wiki 114K 32% www.yahoo.com 321K 13% www.youtube.com 240K 18%

15. splitting the initial payload split your JavaScript between what's needed to render the page and everything else load &quot;everything else&quot; after the page is rendered separate manually (Page Speed); tools needed to automate this (Microsoft Doloto) load scripts without blocking – how?

16. MSN.com: parallel scripts Scripts and other resources downloaded in parallel! How? Secret sauce?! var p= g.getElementsByTagName(&quot;HEAD&quot;)[0]; var c=g.createElement(&quot;script&quot;); c.type=&quot;text/javascript&quot;; c.onreadystatechange=n; c.onerror=c.onload=k; c.src=e; p.appendChild(c) MSN

17. Loading Scripts Without Blocking XHR Eval XHR Injection Script in Iframe Script DOM Element Script Defer document.write Script Tag

18. XHR Eval script must have same domain as main page must refactor script var xhrObj = getXHRObject(); xhrObj.onreadystatechange = function() { if ( xhrObj.readyState != 4 ) return; eval(xhrObj.responseText); }; xhrObj.open('GET', 'A.js', true); xhrObj.send('');

19. XHR Injection var xhrObj = getXHRObject(); xhrObj.onreadystatechange = function() { if ( xhrObj.readyState != 4 ) return; var se=document.createElement('script'); document.getElementsByTagName('head') [0].appendChild(se); se.text = xhrObj.responseText; }; xhrObj.open('GET', 'A.js', true); xhrObj.send(''); script must have same domain as main page

21. Script DOM Element var se = document.createElement('script'); se.src = 'http://anydomain.com/A.js'; document.getElementsByTagName('head') [0].appendChild(se); script and main page domains can differ no need to refactor JavaScript

22. Script Defer <script defer src='A.js'></script> supported in IE and FF 3.1+ script and main page domains can differ no need to refactor JavaScript

23. document.write Script Tag document.write (&quot;<script type='text/javascript' src='A.js'> <script>&quot;); parallelization only works in IE parallel downloads for scripts, nothing else all document.write s must be in same script block

24. browser busy indicators

25. browser busy indicators good to show busy indicators when the user needs feedback bad when downloading in the background

27. Load Scripts Without Blocking * Only other document.write scripts are downloaded in parallel (in the same script block).

28. and the winner is... XHR Eval XHR Injection Script in iframe Script DOM Element Script Defer Script DOM Element Script Defer Script DOM Element Script DOM Element (FF) Script Defer (IE) XHR Eval XHR Injection Script in iframe Script DOM Element (IE) XHR Injection XHR Eval Script DOM Element (IE) Managed XHR Injection Managed XHR Eval Script DOM Element Managed XHR Injection Managed XHR Eval Script DOM Element (FF) Script Defer (IE) Managed XHR Eval Managed XHR Injection Script DOM Element (FF) Script Defer (IE) Managed XHR Eval Managed XHR Injection different domains same domains no order preserve order no order no busy show busy show busy no busy preserve order

30. menu.js image.gif

33. before after menu.js image.gif menu.js image.gif

34. Loading Scripts Without Blocking * Only other document.write scripts are downloaded in parallel (in the same script block). !IE

36. baseline coupling results (not good) * Scripts download in parallel regardless of the Defer attribute. need a way to load scripts asynchronously AND preserve order

49. technique 2: DOM Element and Doc Write Firefox & Opera – use Script DOM Element IE – use document.write Script Tag Safari, Chrome – no benefit; rely on Safari 4 and Chrome 2

52. asynchronous scripts wrap-up

59. performance analyzers (HPWS) YSlow Page Speed Pagetest VRTA neXpert combine JS & CSS X X X use CSS sprites X X use a CDN X X set Expires in the future X X X X X gzip text responses X X X X X put CSS at the top X X put JS at the bottom X avoid CSS expressions X X make JS & CSS external reduce DNS lookups X X minify JS X X X avoid redirects X X X X remove dupe scripts X remove ETags X X X

60. performance analyzers (EFWS) YSlow Page Speed Pagetest VRTA neXpert don't block UI thread split JS payload X load scripts async X inline JS b4 stylesheet X write efficient JS min. uncompressed size optimize images X X shard domains X X flush the document avoid iframes simplify CSS selectors X X

61. performance analyzers (other) YSlow Page Speed Pagetest VRTA neXpert use persistent conns X X X reduce cookies 2.0 X X X avoid net congestion X increase MTU, TCP win X avoid server congestion X remove unused CSS X specify image dims X use GET for Ajax 2.0 reduce DOM elements 2.0 avoid 404 errors 2.0 avoid Alpha filters 2.0 don't scale images 2.0 X optimize favicon 2.0

66. Steve Souders [email_address] http://stevesouders.com/docs/jquery-20090913.ppt