Is React busy when idle?

I’m using React as the UI layer on WebGL Projects.

See for example: https://github.com/dakom/ball-bounce-frp

My concern is that React/ReactDOM might be doing stuff unexpectedly due to the new improvement to take advantage of idle time.

Does React do anything while ReactDOM.render() and setState() are not being called?

[gaearon]

Only if you schedule low-priority work (the exact mechanism is to be determined).

React won’t make random stuff slower by spending idle time just because it can. 😃 The idea is that if something doesn’t need to be synchronous then it’s better to do it in deferred chunks. React won’t create more work for itself out of thin air.

It’s the same amount of work overall, so if it’s not async, then it’s sync and blocks the thread.

[gaearon]

React doesn’t do anything in idle time by default in the version 16.

In the future, reconciliation for some state updates might be deferred to idle time instead of being processed synchronously. There will likely be an API to opt into or out of this, but the specifics aren’t decided on.