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?

我认为JavaScript性能(时间)测试已经足够了。我在这里找到了一篇关于JavaScript性能测试的非常方便的文章。

UX Profiler从用户的角度来解决这个问题。它将所有浏览器事件、网络活动等由用户操作(点击)引起的事件进行分组，并考虑到延迟、超时等所有方面。

您可以使用https://github.com/anywhichway/benchtest，它用性能测试包装了现有的Mocha单元测试。

性能测试最近成了一个流行词，但这并不是说性能测试在QA中不是一个重要的过程，甚至在产品发布之后也不是。当我开发应用程序时，我使用了许多不同的工具，其中一些是上面提到的chrome Profiler，我通常会查看一个SaaS或一些开源的东西，我可以开始工作，然后忘记它，直到我收到警告，说有些东西出了问题。

有很多很棒的工具可以帮助您关注性能，而不需要您跳过一些基本的提醒设置。这里有一些我认为值得你自己去看看。

Sematext.com Datadog.com Uptime.com Smartbear.com Solarwinds.com

为了画出更清晰的画面，这里有一个关于如何为react应用程序设置监控的小教程。

我们总是可以通过简单的date对象来测量任何函数所花费的时间。

var start = +new Date();  // log start timestamp
function1();
var end =  +new Date();  // log end timestamp
var diff = end - start;