Comment by austin-cheney

You can easily prove if the DOM is a performance bottleneck. DOM performance means one of two things: lookup/access speed and render speed. Render speed is only a DOM concern with regard to quantity of nodes and node layering though, as the visual painting to display is a GPU concern.

To test DOM access speed simply compare processing speed during test automation of a large single page app with all DOM references cached to variables versus the same application with no such caching. I have done this and there is a performance difference, but that performance difference cannot be noticed until other areas of the application are very well optimized for performance.

I have also tested performance of node layering and it’s also not what most people think. To do this I used an application that was like desktop UI with many windows that can dragged around each with their own internal content. I found things slowed down considerably when the page had over 10000 nodes displayed across a hundred or so windows. I found this was slower than equivalent desktop environments outside the browser, but not by much.

Most people seem to form unmeasured opinions of DOM performance that do not hold up under tests. Likewise they also fail to optimize when they have the opportunity to do so. In many cases there is active hostility against optimizations that challenge a favorite framework or code pattern.