To be honest, I wrote test 13 myself. I am pretty familiar with Mootools but not with the other libraries in that test hence the errors.
After checking the correct way of modifying the actual DOM nodes content in each library (Mootools: http://jsfiddle.net/ytp5F/ , jQuery: http://jsfiddle.net/VXHPT/ , ExtJS: http://jsfiddle.net/mtZ3y/ ), I rewrote the test: http://jsperf.com/my-js-perf-tests/14 This time, the results certainly are more reasonable... That said, the other JS perf tests created by John-David Dalton (test 1 to 5) are the ones to check out. As a side note, with Mootools, what is the difference between xxx.setProperty('html', '...') and xxx.innerHTML = '...' ?