In all javascript apps the part that is slow is the DOM, not the javascript interface.

This benchmark was taken from the webkit source code then forked into http://vuejs.org/perf/ then forked to include mercury then forked again to include elm.

Neither elm nor mercury came up with this benchmark and just added themself to it.

What this benchmarks shows is that async rendering is really fast. Mercury, vue & elm all use async rendering where DOM effects are batched and only applied once.

A better, close to real user experience benchmark would be one using mousemove since that's an event that can happen multiple times per frame.