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Steve Souders Life's too short, write fast code part 1 Disclaimer: This content does.

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Steve Souders Life's too short, write fast code part 1 Disclaimer: This content does.

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Presentation on theme: "Steve Souders Life's too short, write fast code part 1 Disclaimer: This content does."— Presentation transcript:

1 Steve Souders Life's too short, write fast code part 1 Disclaimer: This content does not necessarily reflect the opinions of my employer.

2 17% 83% iGoogle, primed cache The Importance of Frontend Performance 9%91% iGoogle, empty cache

3 Time Spent on the Frontend Empty CachePrimed Cache search.live.com/results67%0% en.wikipedia.org/wiki94%91% April 2008

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

5 14 Rules 1.Make fewer HTTP requests 2.Use a CDN 3.Add an Expires header 4.Gzip components 5.Put stylesheets at the top 6.Put scripts at the bottom 7.Avoid CSS expressions 8.Make JS and CSS external 9.Reduce DNS lookups 10.Minify JS 11.Avoid redirects 12.Remove duplicate scripts 13.Configure ETags 14.Make AJAX cacheable

6 High Performance Web Sites YSlow

7 June 22-24, 2009

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9 High Performance Web Sites, Vol 2 1.Split the initial payload 2.Load scripts without blocking 3.Don't scatter inline scripts 4.Split dominant domains 5.Make static content cookie-free 6.Reduce cookie weight 7.Minify CSS 8.Optimize images 9.Use iframes sparingly 10.To www or not to www } part 1

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

11 Scripts Block blocks parallel downloads and rendering What's "Cuzillion"?

12 a tool for quickly constructing web pages to see how components interact Open Source Cuzillion 'cuz there are a zillion pages to check

13 JavaScript Functions Executed before onload 9% search.live.com/results17K24% en.wikipedia.org/wiki114K32% 26% avg 252K avg Initial Payload and Execution

14 Split the initial payload split your JavaScript between what's needed to render the page and everything else load "everything else" after the page is rendered separate manually (Firebug); tools needed to automate this (Doloto from Microsoft) load scripts without blocking – how?

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

16 Advanced Script Loading XHR Eval XHR Injection Script in Iframe Script DOM Element Script Defer document.write Script Tag

17 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('');

18 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

19 Script in Iframe

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