更快速网站

内容简介

《更快速网站(影印版)》内容简介：对于任何成功的网站来说，性能是至关重要的。但伴随着不断增长的丰富内容和Ajax的过度使用，如今的Web应用已经将浏览器推至性能极限。在《更快速网站(影印版)》中，Google的Web性能专家和前任雅虎席网站性能官Steve Souders提供了宝贵的技术，来帮助你优化网站性能。
作者的上一《更快速网站(影印版)》是的《High Performance Web Sites》，它透露了80%的网页加载时间是花在客户端，使网络开发世界为之震惊。在《更快速网站(影印版)》中，Souders和8位专家撰稿人提供了*实践和实用建议，用于在三个范畴提高网站的性能：
Javascript——获取用于了解Ajax性能的建议，编写有效的Javascript，创建响应程序，加载脚本时不阻止其他组件等等。
Network——学习穿过多个域共享资源，减小图片尺寸而不损失质量，以及使用分块编码（chunked encoding）来更快呈现页面。
Browser——探索内嵌框架（*）的替代方案、如何简化CSS选择器和其他技术。
对于当今的富媒体网站和Web 2.0应用来说，速度是至关重要的。有了这《更快速网站(影印版)》，你将学习到如何减少你的网站的加载时间，让它们响应得更快。

目录

Credits
Preface
1. Understanding Ajax Performance
Trade-offs
Principles of Optimization
Ajax
Browser
Wow!
Javascript
Summary
2. Creating Responsive Web Applications
What Is Fast Enough?
Measuring Latency
When Latency Goes Bad
Threading
Ensuring Responsiveness
Web Workers
Gears
Timers
Effects of Memory Use on Response Time
Virtual Memory
Troubleshooting Memory Issues
Summary
3. Splitting the Initial Payload
Kitchen Sink
Savings from Splitting
Finding the Split
Undefined Symbols and Race Conditions
Case Study: Google Calendar
4. Loading scripts Without Blocking
scripts Block
Making scripts Play Nice
XHR eval
XHR Injection
script in Iframe
script DOM Element
script Defer
document.write script Tag
Browser Busy Indicators
Ensuring (or Avoiding) Ordered Execution
Summarizing the Results
And the Winner Is
5. Coupling Asynchronous scripts
Code Example: menu.js
Race Conditions
Preserving Order Asynchronously
Technique 1: Hardcoded Callback
Technique 2: Window onload
Technique 3: Timer
Technique 4: script onload
Technique 5: Degrading script Tags
Multiple External scripts
Managed XHR
DOM Element and Doc Write
General Solution
Single script
Multiple scripts
Asynchronicity in the Real World
Google Analytics and Dojo
YUI Loader Utility
6. Positioning Inline scripts
Inline scripts Block
Move Inline scripts to the Bottom
Initiate Execution Asynchronously
Use script Defer
Preserving CSS and Javascript Order
Danger: Stylesheet Followed by Inline script
Inline scripts Aren’t Blocked by Most Downloads
Inline scripts Are Blocked by Stylesheets
This Does Happen
7. Writing Efficient Javascript
Managing Scope
Use Local Variables
Scope Chain Augmentation
Efficient Data Access
Flow Control
Fast Conditionals
Fast Loops
String Optimization
String Concatenation
Trimming Strings
Avoid Long-Running scripts
Yielding Using Timers
Timer Patterns for Yielding
Summary
8. Scaling with Comet
How Comet Works
Transport Techniques
Polling
Long Polling
Forever frame
XHR Streaming
Future Transports
Cross-Domain
Effects of Implementation on Applications
Managing Connections
Measuring Performance
Protocols
Summary
9. Going Beyond Gzipping
Why Does This Matter?
What Causes This?
Quick Review
The Culprit
Examples of Popular Turtle Tappers
How to Help These Users?
Design to Minimize Uncompressed Size
Educate Users
Direct Detection of Gzip Support
10. Optimizing Images
Two Steps to Simplify Image Optimization
Image Formats
Background
Characteristics of the Different Formats
More about PNG
Aut

摘要与插图

Refactoring the code can reduce its apparent complexity， making optimization andother transformations more likely to yield benefits. For example, adopting the YSlowrules can have a huge impact on the delivery time of web pages （see http://developer. yahoo.com/yslow/）.
　　Even so, it is difficult for web applications to get under the Inefficiency line because ofthe size and complexity of web pages. Web pages are big, heavy, multipart things. Pagereplacement comes with a significant cost. For applications where the differencebetween successive pages is relatively small, use of Ajax techniques can produce a significant improvement.
　　Instead of requesting a replacement page as a result of a user action, a packet of datais sent to the server （usually encoded asJSON text） and the server responds with anotherpacket （also typically JSON-encoded） containing data. A Javascript program uses thatdata to update the browsers display. The amount of data transferred is significantly.reduced, and the time between the user action and the visible feedback isalso significantly reduced. The amount of work that the server must do is reduced.The amount of work that the browser must do is reduced. The amount of work thatthe Ajax programmer must do, unfortunately, is likely to increase. That is one of thetrade-offs.
　　The architecture of an Ajax application is significantly different from most other sortsof applications because it is divided between two systems. Getting the division of laborright is essential if the Ajax approach is to have a positive impact on performance. Thepackets should be as small as possible. The application should be constructed as aconversation between the browser and the server, in which the two halves communicatein a concise, expressive, shared language. Just-in-time data delivery allows the browserside of the application to keep n small, which tends to keep the loops fast.
　　A common mistake in Ajax applications is to send all of the applications data to thebrowser. This reintroduces the latency problems that Ajax is supposed to avoid. It alsoenlarges the volume of data that must be handled in the browser, increasing n and againcompromising performance.