jsPerf试试。这是一个在线javascript性能测试工具，用于对代码段进行基准测试和比较。我一直在用它。

剖析器绝对是获取数据的好方法，但根据我的经验，对用户/客户来说，感知性能才是最重要的。例如，我们有一个带有Ext手风琴的项目，它展开来显示一些数据，然后显示一些嵌套的Ext网格。所有内容都呈现得非常快，没有一个操作需要很长时间，只是有很多信息同时呈现，所以用户感觉很慢。

我们“修复”了这个问题，不是通过切换到一个更快的组件，或优化一些方法，而是通过先呈现数据，然后用setTimeout呈现网格。所以，信息先出现，然后网格会在一秒钟后出现。总的来说，这样做需要稍微多一点的处理时间，但对于用户来说，感知性能得到了改善。

如今，Chrome分析器和其他工具普遍可用，而且易于使用 Console.time () (mozilla-docs, chrome-docs) Console.profile () (mozilla-docs, chrome-docs) performance.now () (mozilla-docs) Chrome也给你一个时间轴视图，可以告诉你什么是杀死你的帧率，用户可能在哪里等待，等等。

Finding documentation for all these tools is really easy, you don't need an SO answer for that. 7 years later, I'll still repeat the advice of my original answer and point out that you can have slow code run forever where a user won't notice it, and pretty fast code running where they do, and they will complain about the pretty fast code not being fast enough. Or that your request to your server API took 220ms. Or something else like that. The point remains that if you take a profiler out and go looking for work to do, you will find it, but it may not be the work your users need.

有些人建议使用特定的插件和/或浏览器。我不会，因为它们只对一个平台有用;在Firefox上的测试运行不能准确地转换到IE7上。考虑到99.999999%的网站有多个浏览器访问，您需要检查所有流行平台上的性能。

我的建议是将其保留在JS中。创建一个包含所有JS测试的基准测试页面，并计时执行。您甚至可以使用ajax将结果发送给您，以保持它完全自动化。

然后在不同的平台上重复。

我有一个小工具，可以在浏览器中快速运行小的测试用例，并立即得到结果:

JavaScript速度测试

您可以在测试过的浏览器中测试代码并找出哪种技术更好。

迅速的回答

在jQuery上(更具体地说在Sizzle上)，我们使用这个(签出master并在浏览器上打开speed/index.html)，它反过来使用benchmark.js。这用于对库进行性能测试。

长回答

如果读者不知道基准测试、工作负载和分析器之间的区别，请先阅读spec.org的“readme 1st”部分中的一些性能测试基础知识。这是针对系统测试的，但是理解这个基础也会有助于JS的性能测试。以下是一些最突出的结果:

What is a benchmark? A benchmark is "a standard of measurement or evaluation" (Webster’s II Dictionary). A computer benchmark is typically a computer program that performs a strictly defined set of operations - a workload - and returns some form of result - a metric - describing how the tested computer performed. Computer benchmark metrics usually measure speed: how fast was the workload completed; or throughput: how many workload units per unit time were completed. Running the same computer benchmark on multiple computers allows a comparison to be made. Should I benchmark my own application? Ideally, the best comparison test for systems would be your own application with your own workload. Unfortunately, it is often impractical to get a wide base of reliable, repeatable and comparable measurements for different systems using your own application with your own workload. Problems might include generation of a good test case, confidentiality concerns, difficulty ensuring comparable conditions, time, money, or other constraints. If not my own application, then what? You may wish to consider using standardized benchmarks as a reference point. Ideally, a standardized benchmark will be portable, and may already have been run on the platforms that you are interested in. However, before you consider the results you need to be sure that you understand the correlation between your application/computing needs and what the benchmark is measuring. Are the benchmarks similar to the kinds of applications you run? Do the workloads have similar characteristics? Based on your answers to these questions, you can begin to see how the benchmark may approximate your reality. Note: A standardized benchmark can serve as reference point. Nevertheless, when you are doing vendor or product selection, SPEC does not claim that any standardized benchmark can replace benchmarking your own actual application.

性能测试JS

理想情况下，最好的性能测试是使用自己的应用程序和自己的工作负载来切换需要测试的内容:不同的库、机器等。

如果这是不可行的(通常是不可行的)。重要的第一步:定义您的工作量。它应该反映应用程序的工作负载。在这次演讲中，Vyacheslav Egorov谈到了你应该避免的糟糕工作量。

然后，你可以使用benchmark.js这样的工具来帮助你收集指标，通常是速度或吞吐量。在Sizzle上，我们感兴趣的是比较修复或更改如何影响库的系统性能。

如果某些东西执行得非常糟糕，那么下一步就是寻找瓶颈。

如何找到瓶颈?分析器

分析javascript执行情况的最佳方法是什么?

你可以使用控制台。firebug中的配置文件