Peacekeeper doesn’t test only for JavaScript, it also runs tests for Html5, WebGl, browser-based 3D graphics and video. It’s probably the most polished and complete tool out there.
Peacekeeper is easy to use, just go to their website and click on “Test your browser”, it will take approximately 5 minutes to give you the score based on how the tests went, then you can compare it to results in other machines. If you want to test different browsers in your computer you can repeat the process for each and compare the numbers.
Peacekeeper is the most neutral benchmark tool out there. While other widely used benchmark tools are made by Microsoft, Google or Mozilla and the like, Peacekeeper is developed by a neutral party, this could mean that Peacekeeper is more unbiased in analyzing browser speed and javascript performance.
Unfortunately, Dromaeo does not have an option to save your result in order to compare it to others. The only thing you can do is to bookmark your results and then compare them.
This benchmark tool won’t show you any arbitrary numbers as a result, just the time it took to take each individual test. This is very helpful since it gives you a more detailed view of what is happening behind the scenes and how each browser handles each test.
Unlike other benchmarking tools, SunSpider completely avoids using microbenchmarks, which attempt to test the performance of a "small" amount of code at a time. Instead, SunSpider mostly tries to focus on the problems developers face with JavaScript today, such as generating a tagcloud from a JSON input, 3D raytracer, cryptography tests, code decompression and many more.
Although considered by many to be the most comprehensive benchmark tool out there, the fact that it avoids using microbenchmark to test the code efficiency means that as browsers start to get faster at running day-to-day tasks, SunSpider's tests may start to become easier, especially compared to tools that use microbenchmarks.
To understand how fast this benchmark test is, all you have to do is to open the page. It will immediately give you the score based on it's numerous tests.
Based on the fact that it's made by Google, one of the big guys in the so-called "browser wars" may lead some to think that it may be a little biased towards giving Chrome better results.