Seems like these are two conceptually similar things.
> React traverses the virtual DOM tree to update the UI, resulting in O(n) time complexity.
That's the worst case, on initial load. On most of UI changes nothing stops React to update only local portions of the tree - elements that have their state changed.
Educated guess: In Million and React.JS cases major bottleneck is inside browser re-layout mechanism, not on JS side I think.
In practice, it still re-renders a lot. It’s easy to get a significant performance increase by not using React (usually at least one order of magnitude) - browsers have improved a lot and what looked like an optimization for IE6 is largely overhead now.
Neither framework will fix programmer's errors.
This
for(let child of container)
child.innerHTML = getHtmlFor(i++);
for(let i = 0; i < N; ++i)
html += getHtmlFor(i++);
container.innerHTML = html;
I mean that compiling separate N "small" DOM access calls is not always faster than one integral update.