[masklinn]

Vanilla React doesn't do property diffing by default, it re-renders the whole tree then diffs the whole virtual DOM, because it can't rely on data immutability or on components purity.

Since Om or Elm assume immutable inputs and pure components they can skip rendering components altogether when the inputs have not changed (mentioned in TFA's "Making Virtual DOM Fast").

React can do that, but it has to be opted in component by component either by using PureRenderMixin or by implementing shouldComponentUpdate.

[matchu]

Gotcha—I'd assumed property diffing was the way to go because it hadn't occurred to me that folks would be writing impure components. Thanks!