Narrow Effect Dependencies
Specify primitive dependencies instead of objects to minimize effect re-runs.
Incorrect (re-runs on any user field change):
useEffect(() => {
console.log(user.id)
}, [user])Correct (re-runs only when id changes):
useEffect(() => {
console.log(user.id)
}, [user.id])For derived state, compute outside effect:
// 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])