In the first part of the talk, John reviewed the range of tools available to frontend engineers for unit testing and for analyzing the performance of code. In the latter case, he argues for going beyond pure speed-based benchmarks to structural analyses of performance. By looking at structure, the jQuery team was able to identify and correct bottlenecks, resulting in major performance improvements in the upcoming 1.4 release. In the second part of the talk (beginning at 49:20 in the video), John reviews some of those jQuery 1.4 changes. In the short third section (beginning at 1:03:15), he looks at some interesting trends he’s noticed in the practical application of new HTML 5 elements — especially in older browsers.