React docs oversell this point a bit: https://facebook.github.io/react/docs/multiple-components.ht...

"You may be thinking that it's expensive to change data if there are a large number of nodes under an owner. The good news is that JavaScript is fast and render() methods tend to be quite simple, so in most applications this is extremely fast. Additionally, the bottleneck is almost always the DOM mutation and not JS execution. React will optimize this for you by using batching and change detection. [...] Don't underestimate how fast JavaScript is relative to the DOM."