Narrow Effect Dependencies
Specify primitive dependencies instead of objects to minimize effect re-runs.
Incorrect (re-runs on any user field change):
tsx
useEffect(() => {
console.log(user.id);
}, [user]);
Correct (re-runs only when id changes):
tsx
useEffect(() => {
console.log(user.id);
}, [user.id]);
For derived state, compute outside effect:
tsx
// Incorrect: runs on width=767, 766, 765...
useEffect(() => {
if (width < 768) {
enableMobileMode();
}
}, [width]);
// Correct: runs only on boolean transition
const isMobile = width < 768;
useEffect(() => {
if (isMobile) {
enableMobileMode();
}
}, [isMobile]);