While it's nice that Ember.js provides a run loop that's not enough, just batching all your updates into one place just puts all of the work together, you'll still going to pay for the work and in the worse case you have to hand coalesce, yuck. In Om if there is no work ... there is no work, it's implicit in the system! No need for hand coalescing your state changes.

Angular.js still suffers as shown by the optimization article I linked to in my post. These kinds of typical optimizations can and should be pushed out of the user's hands.

You're misunderstanding. There's no hand coalescing in Ember, and there's no duplicate work. If you change your models a thousand times in a row, you still get one redraw, fully automatically.

The same holds for dependent computed properties. If you change a dependencies many times in a row, the dependent property only reevaluates once.

If that's really true for Ember.js that's great! I'm curious as to why it performs so badly? http://www.petehunt.net/react/tastejs/benchmark.html

I looked at that benchmark and there's a few huge red flags right away:

1. It's not running Ember in production mode which is much faster.

2. It's running an older release candidate version of Ember.

3. It is purposely wrapping individual events in run loop executions rather than just letting ember figure out when you put things into run loops.

I re-ran the benchmarks with the latest production mode Ember.js and removed the incorrect run loop usage got the following results:

https://gist.github.com/eviltrout/8058560

It's still slower than ReactJS but much less so than before. In fact it's now #3 in that benchmark suite behind ReactJS and Backbone (and much faster than ReactJS in the completing benchmark), although I wouldn't be surprised if the other frameworks were set up as incorrectly too.

Thanks for the clarifications!

How does the performance of this compare to AngularJS? Also a common performance issue in AngularJS is when there are too many watchers (such as a large table with many rows and columns) which causes the $digest to become really slow. Would Om/React avoid these kind of performance issues?

Yeah, I think it's rather misleading to compare om to the performance of the least optimized and most naive (on purpose, mind you) framework instead of a more robust one.

There are benchmarks comparing vanilla React to other frameworks: http://facebook.github.io/react/blog/#todomvc-benchmarks

At least according to this data, React and Backbone are the fastest. (Om is faster than vanilla React)

One suspects that with hand-optimization the other frameworks could be a lot faster, but the point of this post is that it is fast without hand-optimizations.

Keep in mind that those benchmarks don't use the requestAnimationFrame() batching strategy (out-of-the-box it's not installed since it makes testing harder since you have to wait for the next frame) like swannodette mentions.

I'd be interested to see these numbers after doing `npm install react-raf-batching` and doing `require('react-raf-batching').install()`.

In general "faster without optimization" is completely meaningless because it doesn't mean fast with optimization, which is what actually matters.

Example: Average code written in node.js is typically just as slow as, say, PHP (in fact node.js was 3x slower than php in techempower benchmarks). However, it has potential to be much faster when optimized whereas PHP doesn't reward such optimization almost at all.