Why I used these tests
Most of the performance tests in the wild do not render anything during the test when it comes to DOM or CSS manipulation. My tests do.
Several browsers are quite fast while they run JS scripts without the need to care about visual DOM or CSS changes but eventually break down as soon as they have to render it to the screen. Performing DOM and CSS manipulations on non-visual elements is by far faster but does not measure the real impact those manipulations have on the visual user experience.
The tests utilize a broad variety of math object calls, array manipulations, bit shifting, time object calls, timeouts, intervals, function calls and other common things used on web pages in combination in a more or less real world mix and do not perform the same short action over and over again in a loop like some other tests do. Heavy use of math.random provides additional variances so that caching effects are mostly mitigated.
Of course these tests do not test the full spectrum of JS, HTML, DOM or CSS manipulations, but they were never meant to do so. They just show an aspect that many other tests do not show:
Interaction of browser "modules" while displaying what happens.