How do you performance test JavaScript code?

Question

CPU Cycles, Memory Usage, Execution Time, etc.?

Added: Is there a quantitative way of testing performance in JavaScript besides just perception of how fast the code

Answer 1

Some people are suggesting specific plug-ins and/or browsers. I would not because they're only really useful for that one platform; a test run on Firefox will not translate accurately to IE7. Considering 99.999999% of sites have more than one browser visit them, you need to check performance on all the popular platforms.

My suggestion would be to keep this in the JS. Create a benchmarking page with all your JS test on and time the execution. You could even have it AJAX-post the results back to you to keep it fully automated.

Then just rinse and repeat over different platforms.