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Comment by acdha | Hacker News Reader

> On most of UI changes nothing stops React to update only local portions of the tree - elements that have their state changed.

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.

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> In practice, it still re-renders a lot.

Neither framework will fix programmer's errors.

This

   for(let child of container)
      child.innerHTML = getHtmlFor(i++);

will always be slower than this:

   for(let i = 0; i < N; ++i)
      html += getHtmlFor(i++);
   container.innerHTML = html;

N transactions versus 1 transaction.

I mean that compiling separate N "small" DOM access calls is not always faster than one integral update.

My point was that that is enormously slower than storing a reference to the elements when you create them and setting only the specific attributes which changed. innerHtml string parsing forces the browser to do too much work unless you’re literally changing everything. Each time I’ve replaced that with DOM operations it’s been an order of magnitude or more performance gain - on one project, getting rid of fully-optimized React was 4 orders, but I think they’ve optimized it enough since then that it’s only 1-2.

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