Side Effects with useEffect

Synchronise a component with the outside world: how effects run, what the dependency array really means, why cleanup matters, and when not to use an effect at all.

Level

Intermediate

Chapters

4

Exercises

1

Reading time

18 min

What you will cover

1. 1. What an Effect IsSynchronising with systems outside React, and when the effect body runs.
2. 2. The Dependency ArrayThe three forms of the second argument and what each one means.
3. 3. CleanupReturning a teardown function, and why React runs it more often than you expect.
4. 4. When Not to Use an EffectThe four cases where an effect is the wrong tool, and what to do instead.

Up next after this one: Refs with useRef