[翻译]High Performance JavaScript(027)
第九章
Building and Deploying High-Performance JavaScript Applications
创建并部署高性能JavaScript应用程序
According to a 2007 study by Yahoo!'s Exceptional Performance team, 40%–60% of Yahoo!'s users have an empty cache experience, and about 20% of all page views are done with an empty cache (http://yuiblog.com/blog/2007/01/04/performance-research-part-2/). In addition, another more recent study by the Yahoo! Search team, which was independently confirmed by Steve Souders of Google, indicates that roughly 15% of the content delivered by large websites in the United States is served uncompressed.
根据Yahoo!卓越性能团队在2007年进行的研究，40%-60%的Yahoo!用户没有使用缓存的经验，大约20%页面视图不使用缓存（http://yuiblog.com/blog/2007/01/04/performance-research-part-2/）。另外，由Yahoo!研究小组发现，并由Google的Steve Souders所证实的一项最新研究表明，大约15%的美国大型网站所提供的内容没有压缩。
These facts emphasize the need to make sure that JavaScript-based web applications are delivered as efficiently as possible. While part of that work is done during the design and development cycles, the build and deployment phase is also essential and often overlooked. If care is not taken during this crucial phase, the performance of your application will suffer, no matter how much effort you've put into making it faster.
这些事实强调有必要确保那些基于JavaScript的网页应用尽量高效地发布。虽然部分工作在设计开发过程中已经完成，但构建和部署过程也很重要且往往被忽视。如果在这个关键过程中不够小心，你应用程序的性能将受到影响，无论你怎样努力使它更快。
The purpose of this chapter is to give you the necessary knowledge to efficiently assemble and deploy a JavaScript-based web application. A number of concepts are illustrated using Apache Ant, a Java-based build tool that has quickly become an industry standard for building applications for the Web. Toward the end of the chapter, a custo
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本文主要是出于有朋友使用我原来写的autocomplete的JS控件。当数据量大的时候，会出现效率极其慢的情况，我在这段时间做出的一些测试也及一些经验，与大家分享，如果有错的地方，还请指出。
经过测试，我们会发现如下的情况或者说的结论，如果您的测试结果与我的不符，请说明原因，以便相互学习。
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Repaints and Reflows 重绘和重排版
Once the browser has downloaded all the components of a page—HTML markup, JavaScript, CSS, images—it parses through the files and creates two internal data structures:
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Data Formats 数据格式
When considering data transmission techniques, you must take into account several factors: feature set, compatibility, performance, and direction (to or from the server). When considering data formats, the only scale you need for comparison is speed.
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