[翻译]High Performance JavaScript(032)
Fiddler
Fiddler is an HTTP debugging proxy that examines the assets coming over the wire and helps identify any loading bottlenecks. Created by Eric Lawrence, this is a general purpose network analysis tool for Windows that provides detailed reports on any browser or web request. Visit http://www.fiddler2.com/fiddler2/ for installation and other information.
Fiddler是一个HTTP调试代理，检查资源在线传输情况，以定位加载瓶颈。它由Eric Lawrence创建，是一个Windows下通用的网络分析工具，可为任何浏览器或网页请求给出详细报告。其安装和其它信息参见http://www.fiddler2.com/fiddler2/。
During installation, Fiddler automatically integrates with IE and Firefox. A button is added to the IE toolbar, and an entry is added under Firefox's Tools menu. Fiddler can also be started manually. Any browser or application that makes web requests can be analyzed. While running, all WinINET traffic is routed through Fiddler, allowing it to monitor and analyze the performance of downloaded assets. Some browsers (e.g., Opera and Safari) do not use WinINET, but they will detect the Fiddler proxy automatically, provided that it is running prior to launching the browser. Any program that allows for proxy settings can be manually run through Fiddler by pointing it at the Fiddler proxy (127.0.0.1, port: 8888).
在安装过程中，Fiddler与IE和Firefox自动集成。IE工具栏上将添加一个按钮，Firefox的工具菜单中将增加一个菜单项。Fiddler还可以手工启动。任何浏览器或应用程序发起的网页请求都能够分析。它运行时，所有WinINET通信都通过Fiddler进行路由，允许它监视并分析资源下载的性能。某些浏览器（例如Opera和Safari）不使用WinINET，但它们会自动检测Fiddler代理，倘若它在浏览器启动之前正在运行的话。任何能够设置代理的程序都可以手工设置指定它使用Fiddler代理（127.0.0.1，端口：8888）。
Like Firebug, Web Inspector, and Page Speed, Fiddler provides a waterfall diagram that provides insights as to which assets are taking longer to load and
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function total(){
var i=0;
for(j=1;j<=20;j++)
{
var step="step"+j;
if(document.getElementById(step)){
if(document.getElementById(step).checked==true)
{
i=i+parseInt(document.getElementById(step).value);
}
}
}
document.getElementById("total").innerHTML = i;
}
function Resetvalue(){
......
Recursion Patterns 递归模式
When you run into a call stack size limit, your first step should be to identify any instances of recursion in the code. To that end, there are two recursive patterns to be aware of. The first is the straightforward recursive pattern represented ......
Regular Expression Optimization 正则表达式优化
Incautiously crafted regexes can be a major performance bottleneck (the upcoming section, "Runaway Backtracking" on page 91, contains several examples showing how severe this can be), but there is a lot you can do to improve re ......
第十章 Tools 工具
Having the right software is essential for identifying bottlenecks in both the loading and running of scripts. A number of browser vendors and large-scale websites have shared techniques and tools to help make the Web faster and more efficient. This ......
