HighPerformanceWebSites

Googlecom an example of minied library is yuis pure at

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Unformatted text preview: ype="text/css" title="alt2" media="screen" /> function changeStyle(title) { var lnks = document.getElementsByTagName('link'); for (var i = lnks.length - 1; i >= 0; i--) { if (lnks[i].getAttribute('rel').indexOf('style')> -1 && lnks[i].getAttribute('title')) { lnks[i].disabled = true; if (lnks[i].getAttribute('title') == title) lnks[i].disabled = false; } } } <span onclick="changeStyle('alt2')">Switch to second alternative stylesheet</span> Copyright 2009 - 2013 Horowitz 19 Rule 6: Move Scripts to the Bolom •  As the loading of JavaScript can cause the browser to stop rendering the page unOl the JavaScript is fully loaded, one can avoid the delay by moving scripts to the bolom •  A second opOon is the defer alribute <script type="text/javascript" defer="defer"> some script .... </ script> •  Defer indicates that the script is not going to generate any document content. The browser can conOnue parsing and drawing the page Copyright 2009 - 2013 Horowitz 20 Rule 7: Avoid CSS Expressions •  Used to set CSS properOes dynamically in IE Width: expression(document.body.clientWidth < 600 ? “600px” : “auto”); •  Problem: expression may execute many Omes –  Mouse moves, key press, resize, scroll, etc •  AlternaOves –  One- Ome expressions –  Event handlers •  Expression overwrites itself <style> P { background-color: expression(altBgcolor(this)); } </style> <script> function altBgcolor(elem) { elem.style.backgroundColor = (new Date()).getHours()%2 ? “F08A00” : “#B8D4FF”; } </script> Copyright 2009 - 2013 Horowitz 21 Rule 8: Make JS and CSS External •  JavaScript can be placed inline, e.g <script type=“text/javascript>var foo = “bar”; </script> •  Or as an external script, e.g. <script src=“foo.js” type=“text/javascript”></script> •  Placing JavaScript and CSS inline makes the docu...
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This note was uploaded on 01/29/2014 for the course CSCI 571 taught by Professor Papa during the Spring '07 term at USC.

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