书籍介绍
如果说第一本《高性能网站建设指南》告诉你'网页加载时间占了用户等待的八成'，那么这本书则把读者推到了更深的困境里：当Ajax让页面变得'活'起来，它同时也把浏览器逼进了能力极限。本书最见功力的地方，在于它不满足于'把图片压小'这类表层技巧，而是逼你直面一个残酷现实——JavaScript的执行会阻塞下载、阻塞渲染，甚至让整个页面在开始显示前就卡顿。书中对无阻塞加载脚本的拆解堪称精华：从XHR注入到Script DOM，从DEFER属性到异步回调，每一步都伴随着'为什么'的追问。它适合那些已经踩过性能坑、愿意为毫秒较真的前端开发者；也提醒所有人：优化没有终点，其上限取决于你对底层机制的理解深度。
作者简介
Steve Souders现在Google工作，负责Web性能和开源组织。他是Firebug的性能分析扩展YSlow的创建者，也是O’Reilly Web性能与运作会议Velocity的联合主席。Steve经常在技术会议和诸如Microsoft、Amazon、MySpace、
LinkedIn和Facebook这样的知名高科技公司发表演讲。
特约作者：
Dion Almaer, Douglas Crockford,
Ben Galbraith, Tony Gentilcore,
Dylan Schiemann, Stoyan
Stefanov, Nicole Sullivan, and
Nicholas C. Zakas
AI导读
核心看点
- 本书深入剖析JavaScript性能优化，详细讲解无阻塞加载脚本、拆分初始化负载及创建快速响应应用的技术。作者Steve Souders揭示了浏览器解析脚本时的阻塞机制，并提供XHR注入、Script DOM Element等具体方案，帮助开发者解决脚本加载导致的页面渲染延迟问题，确保应用流畅运行。
- 内容涵盖网络层与浏览器渲染优化，包括跨域资源共享、图片无损压缩、块编码加速渲染及CSS选择符简化。书中强调避免iframe滥用，指导开发者通过合法合规的技术手段提升传输效率，减少不必要的网络请求与资源浪费，从底层架构上提升网站整体加载速度与用户体验。
- 作为《高性能网站建设指南》的续作，本书聚焦Web 2.0富媒体应用的性能瓶颈。通过Google日历等真实案例，展示如何在复杂交互场景下平衡功能与性能。书中提供的最佳实践旨在帮助开发者理解浏览器工作原理，规避内存泄漏与竞争状态，构建符合现代Web标准的高性能应用。
读者共识
- 读者普遍认为本书是前端性能优化领域的经典之作，尽管部分技术细节已随时代发展而过时，但其核心思想与优化原则依然具有极高的参考价值。许多资深开发者表示，书中关于JavaScript执行机制、浏览器渲染原理的深入剖析，帮助他们从根本上理解了性能瓶颈的成因，提升了技术视野与问题解决能力。
- 部分读者指出，本书内容过于专业且部分案例陈旧，不适合初学者或初级开发者阅读。有评论认为书中某些技术如Gears已彻底淘汰，直接应用可能导致兼容性问题。然而，也有读者强调，学习此类经典著作的意义在于掌握性能优化的思维方式，而非具体代码，建议读者取其精华，结合现代技术进行创新应用。
- 读者高度认可本书对Web标准与安全性的重视，认为其提供的优化建议均建立在合法合规的基础上。尽管存在技术过时的争议，但书中关于避免阻塞、减少请求、优化资源加载等原则，至今仍被广泛认可并应用于现代前端开发中。许多读者表示，反复阅读本书有助于巩固性能意识，避免在复杂项目中陷入性能陷阱。
精彩摘录
- "Timers are the de facto standard for splitting up JavaScript code execution in browsers. Whenever a script is taking too long to complete, look to delay parts of the execution until later. Note that very small timer delays can also cause the browser to become unresponsive. It’s recommended to never "
- "by default, all functions passed into setTimeout are run in the global context, so this is equal to window."
- "Normally, most browsers download components in parallel, but that’s not the case for external scripts. When the browser starts downloading an external script, it won’t start any additional downloads until the script has been completely downloaded, parsed, and executed. (Any downloads that were alrea"
- "The DEFER attribute is an easy way to avoid the bad blocking behavior of scripts with the addition of a single word: <script defer src='A.js'></script> Although DEFER is part of the HTML 4 specification, it is implemented only in Internet Explorer and in some newer browsers."
- "There is a drawback to the synchronous loading of script blocks: If lots of code has to be downloaded and executed while parsing the head of the document, there might be a noticeable lag before the page begins to render. To alleviate this, we could have used the defer attribute on script elements. T"
- "While the inline script is executing, all other downloads are blocked. ... In addition to blocking parallel downloads, inline scripts block rendering. ... If your site uses inline scripts, it’s important to understand how they block downloads and rendering, and to avoid this behavior if possible. Se"
- "Preserving the order of JavaScript is critical, and this is true for CSS as well. Given the cascading nature of styles, loading them in different orders may yield undesired results. To provide consistent behavior, browsers ensure that CSS is applied in the order speci- fied. The Stylesheets in Order"
- "In the previous section, we confirmed that browsers apply CSS (stylesheets as well as inline styles) in the order in which they appear in the HTML document. Earlier in this chapter, we verified that inline scripts block other browser activity (downloads and rendering). These insights are fairly well"
目录
用户评论
好好实践吧
不错书，有些东西之前没考虑过
手册
mind blowing
很长见识。这样的书应该多搞一些。
可以了解到很多原理性的内容
为了做PPT迅速过一遍，适合做成blog，写书太单薄了。
特别好的工具书，可以用来做性能优化
快速翻了下，先了解一些概念。
随着互联网的发展 网站性能优化的手段也有发展
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