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I wondered about this too, in general I think the article misses that updating state is the key to "causing" effects. Rather than latching onto the callback model to explicitly "run" effects.

Though I'll admit getting the relationship of state and effects caused by changes to that state can be more difficult to work out mentally, I think it results in a more complete understanding of what a component actually does.




I agree it's not intuitive at first. As someone pointed out on Twitter (can't find link at the moment):

A good mental model is that the second argument to useEffect defines which pieces of state that effect syncs with.

useEffect(() => {}, undefined) // Sync with all state

useEffect(() => {}, []) // Sync with no state

useEffect(() => {}, [a, b]) // Sync with `a` & `b`


Original source was Ryan Florence:

https://twitter.com/ryanflorence/status/1125041041063665666




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