Timing of effects

Although useEffect is deferred until after the browser has painted, it's guaranteed to fire before any new renders. React will always flush a previous render's effects before starting a new update.

Is this true in both concurrent and non-concurrent mode. It would appear intuitively that these two call-sites in non-concurrent mode would be deterministic:

ReactDOM.render(<Foo>, container)
ReactDOM.render(<Foo>, container)

That is it would invoke a new render before the effect in the first render has been invoked.

If so would it make more sense to specify it is only in relation to effects i.e previous effects are guaranteed to run before future effects.

As it stands, it looks appears as though the "render" call-site is non-deterministic in non-concurrent.

まず、エフェクトが新しいレンダーの前にフラッシュされるという、引用されたドキュメントの記述を確認し、その後、その文言を2か所のReactDOM.renderの呼び出し箇所、およびconcurrentとnon-concurrentの両方の動作と比較します。ドキュメントがサポートされる保証を明確に記載し、それがレンダー全般に適用されるのか、エフェクトの順序にのみ適用されるのかを明らかにできれば完了です。