A lire dans Tendances n°23, le magazine du Conseil de développement de Loire-Atlantique
Via vincent lecourt
EcoConception Logicielle
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Green IT, performance web, économies d'énergies, bref : éco-conception logicielle !
Curated by
Mickael Ruau
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In this article we're going to cover some common, and not so common smart JavaScript techniques and patterns to improve your code in both size and beauty. 
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Google vient de mettre à jour l'interface de PageSpeed Insights de manière à afficher encore plus dynamiquement et rapidement le respect des bonnes pratiques de Performance Web d'un site web.
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Les meilleurs endroits et ressources pour recycler vos ordinateurs moins performants et vos vieux mobiles ou faire une demande d’équipements.
Mickael Ruau's insight:
Annuaires Don Ordi : Annuaire des organismes récupérant les ordinateurs inutilisésOrdi 2.0 avec une carte pour trouver les reconditionneurs en France
Ressources fédératives Informations
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Too much 3rd Party content can slow down the growth of your site, reduce engagement, conversions and more. Learn how you can still incorporate widgets, plugins etc and still have a site that does not force your visitors to leave and never return.
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Link prefetching is a browser mechanism, which utilizes browser idle time to download or prefetch documents that the user might visit in the near future.
Mickael Ruau's insight:
<!-- full page --> <link rel="prefetch" href="http://davidwalsh.name/css-enhancements-user-experience"; /> <!-- just an image --> <link rel="prefetch" href="http://davidwalsh.name/wp-content/themes/walshbook3/images/sprite.png"; />
HTML5 prefetching is done via the LINK tag, specifying "prefetch" as the rel and the href being the path to the document. Mozilla also answers to a few differently named LINK rel attributes: <link rel="prefetch alternate stylesheet" title="Designed for Mozilla" href="mozspecific.css" /> <link rel="next" href="2.html" />HTTPS fetches are also supported.
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CSS grids can improve performance? How so?
Mickael Ruau's insight:
Finding common denominators in our site will allow us to standardize the way we group related content, and the classes we use to style that content. You can think of these common denominators as the semantic building blocks of a high performance website. On a basic level that means that most sites have a particular way of displaying, for instance, a product. Perhaps with an image of the product to the left and a description of the product to the right. If that configuration appears throughout the site it should not be rewritten each time or we’ll have a 1:1 correlation between the size of the CSS and the complexity or number of pages in the site. These are the kind of sites that might start off fast but over the course of their lifetime become slower and slower. Once clean CSS becomes bloated with unnecessary recoding of semantically and visually identical elements.
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What is the internet made of? At least the UI layer is mainly composed of media blocks. I talked about the Facebook stream story before, and all the tiny objects of which it is composed. For the most part, the stream story is made up of the media object repeated over and over.
Mickael Ruau's insight:
It is a very simple object, but it is very powerful. We can eliminate a lot of lines of code abstracting this repeating pattern. The code for the media block and many other “web Lego” are available on the Object Oriented CSS open source project.
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Learn how to create menu rollovers with different graphic backgrounds with one image. Save HTTP requests by combining on and off images into one mini-sprite and position with CSS.
Mickael Ruau's insight:
CSS is traditionally used to create rollover effects with two or more images for menus and other elements. Menus can use on, off, or visited images to signify the state of the menu. Typically menus are created using multiple background images, however. The problem with this method is that it doubles the necessary HTTP requests and can cause flickering problems when the "off" image is not preloaded. A better way is to combine the on and off state images into one mini-sprite and switch the background position on rollover (see Figure 1).
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Which program is the alpha transparency dog of PNG optimization? We put the front runners of the photo optimization pack through their paces.
Mickael Ruau's insight:
Over 60% of the file size of the average web page is taken up by graphics and multimedia. So graphics optimization is an important step in optimizing web page speed. At an alarming frequency, we have seen large PNG24 and unoptimized JPEGs used on the Web. Large PNG24s should be optimized for file size or converted to PNG8s. This article shows how to optimize PNG files effectively by minimizing their color palettes, and using alpha transparency intelligently.
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Noise is the enemy of efficient multimedia optimization. Learn how to minimize the noise in your images and videos to maximize compression.
Mickael Ruau's insight:
Noise is the enemy of multimedia compression. Avoid introducing noise into your images, both still and motion, by using high quality equipment, saving high quality output, and working from originals. Noise can increase the size of JPEGs by up to 20% to 30%, and palette-based images by a factor of 100. You can remove noise most effectively with specialized noise reduction software. Removing noise can save over 50% in file size.
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You can improve HTTP compression by using all lowercase markup. We test five popular sites for improved compression. Remember, all characters are not created equal.
Mickael Ruau's insight:
The GZIP compression algorithm used in mod_gzip and other HTTP compression programs works by substituting shorter tokens for longer identical strings. By using more lowercase strings, especially repetitious table and div structures, you increase the likelihood of more string matches. While an HTML file of all lowercase markup is the same size as a mixed case HTML file, it compresses more efficiently. Even if you don't use HTTP compression on your site, your users on dialup accelerators like Earthlink's Accelerator and AOL's Topspeed will benefit from your lowercase markup.
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Conditional SSI let you deliver customized content to different browsers and platforms without requiring additional HTTP requests. With conditional CSS, you can include additional styles for modern browsers, without upsetting older ones.
Mickael Ruau's insight:
You can minimize HTTP requests by combining external CSS and JavaScript files. You can go even further by server-side including the remaining external files (with restrictions for XHTML due to its XML nature). One additional technique is to make those SSI work harder for you by serving up conditional content. Conditional server-side includes let you deliver different content based on environment variables sent by browsers to servers.
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Annyang est une bibliothèque Javascript permettant d'ajouter de la reconnaissance vocale sur ses pages web afin d'ajouter des contrôles et navigation interactifs.
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Un guide complet sur la compression d'image pour le web.
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Faut-il investir dans l'optimisation du code ou l'achat de matériel puissant ?
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"Récemment rebaptisée « Lahso », l’association de l’hôtel social est une structure lyonnaise fondée en 1968 qui vient en aide aux publics défavorisés. Réparti sur 4 sites, les 80 collaborateurs de Lahso viennent de réaliser un grand saut numérique : tous les collaborateurs disposent désormais de leur propre environnement informatique sur lequel ils peuvent travailler de façon complètement indépendante du lieu ou du terminal utilisé." Via @Chuchoteuse d'Alternatives
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Clone an array or copy an array using JavaScript using the slice method. The slice(0) method allows developers to copy and clone arrays.
Mickael Ruau's insight:
To clone the contents of a given array, all you need to do is call slice, providing 0 as the first argument: var clone = myArray.slice(0);The code above creates clone of the original array; keep in mind that if objects exist in your array, the references are kept; i.e. the code above does not do a "deep" clone of the array contents. To add clone as a native method to arrays, you'd do something like this: Array.prototype.clone = function() { return this.slice(0); };And there you have it! Don't iterate over arrays to clone them if all you need is a naive clone!
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Facebook crée son datacenter à partir des technologies open source et réalise d'importantes économies financières et d'énergie De nos jours, l'utilisation des datacenters par les grosses entreprises de l'informatique comme Facebook et bien...
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We talked about our experiences optimizing large-scale sites like Facebook and Yahoo!, and we discussed our findings regarding the CSS efficiency of the Alexa Top 1000 websites.
Mickael Ruau's insight:
Happy perf optimizing!
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Mickael Ruau's insight:
Une conception objet du code css permet de rendre le code plus compact et performant.
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Learn how to create optimized drop-shadows in Photoshop to minimize the size of web graphics.
Mickael Ruau's insight:
In summary, use the following techniques to simplify your drop shadows. Use Layer Styles to create and tweak drop shadowsIncrease opacity (darker is better)Reduce Drop Shadow Distance and SizeRemove Anti-Aliasing or use Sharp Anti-AliasingUse Sans-Serif FontsUse a Solid Drop ShadowWhat about CSS Drop ShadowsThis tutorial showed how to create drop shadows that create smaller web graphics. Many of these techniques can be applied to non-text layers. You can also use CSS to create drop shadows for text
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Many email programs and gateways have size limits on attachments. Learn how to split larger PDF files into smaller ones using PDF tools.
Mickael Ruau's insight:
The average web page is now over 1MB in size, with each of its various components increasing in file size as well (HTTPArchive.org June 2012). PDFs can become so large that some email programs and gateways will not allow them to pass (with 5MB or 10MB file size limits). This article shows how you can efficiently split your PDF into multiple files to fit within the 5-10MB email gateway limits.
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This article is a description of the optimization of the html of Webreference.com
Mickael Ruau's insight:
Browser interact with servers in discrete-sized packets. By minimizing the size of your page's HEAD, you can speed your content's initial display. The HEAD must be parsed before the rest of the page is rendered.
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Shorthand hex notation substitutes 3-character color values for 6-character colors when each of the color channels is identical in an RRGGBB hex triplet.
Mickael Ruau's insight:
Shorthand hex notation abbreviates 6-character RRGGBB CSS colors into 3-character RGB shorthand. Combined with shorthand properties and grouping, shorthand hexadecimal colors can shrink style sheets dramatically, often by 50%.
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Les TICs sont-elles aussi « vertes » que les fabricants le revendiquent ? Permettent-elles de réduire la pression sur les ressources ? De réduire la production de gaz à effet de serre (GES) ? De faire des économies ? Françoise Berthoud, ingénieure de recherche au Laboratoire de Physique et Modélisation des Milieux Condensés (CNRS Grenoble) apporte ses réponses