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.

Comece revisando a afirmação citada na documentação sobre os efeitos serem liberados antes de novas renderizações e, em seguida, compare sua redação com os dois locais de chamada de ReactDOM.render e com o comportamento tanto concurrent quanto non-concurrent. O trabalho estará concluído quando a documentação declarar claramente a garantia oferecida e esclarecer se ela se aplica às renderizações em geral ou apenas à ordenação dos efeitos.