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React

612What the Dependency Array Actually Does
613The eslint-plugin-react-hooks/exhaustive-deps Rule
614Why Missing Dependencies Break Your Effects
615The Classic Stale Closure Bug
616Functions in Dependencies: The Problem
617Wrapping Functions with useCallback
618Moving Functions Inside Effects
619The useEffectEvent Proposal (React Labs)
620When to Ignore the Exhaustive-Deps Warning
621Ref Values Don't Belong in Dependencies
622Debugging Missing Dependency Issues
623The Classic Infinite Loop: setState in Effect Body
624Object Dependencies Causing Loops
625Function Dependencies That Recreate Every Render
626State Updates Based on State Without Functional Form
627Derived Values as Dependencies
628Missing Memoization on Complex Dependencies
629The Empty Dependency Array Escape Hatch Gone Wrong
630Props as Dependencies: The Unstable Reference Problem
631Debugging Infinite Loops with Console Logs
632Using useRef to Break the Loop
633Why Objects in Dependencies Cause Re-runs
634The Inline Object Antipattern
635The Inline Array Antipattern
636Moving Objects Outside the Component
637useMemo for Derived Objects
638Destructuring Object Props in Dependencies
639JSON.stringify as a Last Resort
640Arrays from .map and .filter
641Stable References with useCallback
642Client-Side Fetching: The Hidden Cost
643The Waterfall Problem
644Server Components: Fetch Before Rendering
645SSR with Loaders: Next.js and Remix Patterns
646When Client Fetching is Actually Right
647The SEO and Performance Impact
648Migration Strategy: Moving Fetches Server-Side
649What 'Deriving State' Means
650The Symptom: Stale Derived Values
651Example: Filtering Props in an Effect
652Why It's Wrong: Double Rendering
653The Fix: Compute During Render
654When Computation is Expensive: useMemo
655Recognizing the Pattern in the Wild
656Exception: External System Synchronization
657Events vs Effects: The Fundamental Distinction
658The 'Handle Event in Effect' Antipattern
659Moving onClick Logic Out of Effects
660Form Submission: Event Handler, Not Effect
661The 'Derived Trigger' Problem
662Refactoring: From Effect to Direct Call

React

612What the Dependency Array Actually Does
613The eslint-plugin-react-hooks/exhaustive-deps Rule
614Why Missing Dependencies Break Your Effects
615The Classic Stale Closure Bug
616Functions in Dependencies: The Problem
617Wrapping Functions with useCallback
618Moving Functions Inside Effects
619The useEffectEvent Proposal (React Labs)
620When to Ignore the Exhaustive-Deps Warning
621Ref Values Don't Belong in Dependencies
622Debugging Missing Dependency Issues
623The Classic Infinite Loop: setState in Effect Body
624Object Dependencies Causing Loops
625Function Dependencies That Recreate Every Render
626State Updates Based on State Without Functional Form
627Derived Values as Dependencies
628Missing Memoization on Complex Dependencies
629The Empty Dependency Array Escape Hatch Gone Wrong
630Props as Dependencies: The Unstable Reference Problem
631Debugging Infinite Loops with Console Logs
632Using useRef to Break the Loop
633Why Objects in Dependencies Cause Re-runs
634The Inline Object Antipattern
635The Inline Array Antipattern
636Moving Objects Outside the Component
637useMemo for Derived Objects
638Destructuring Object Props in Dependencies
639JSON.stringify as a Last Resort
640Arrays from .map and .filter
641Stable References with useCallback
642Client-Side Fetching: The Hidden Cost
643The Waterfall Problem
644Server Components: Fetch Before Rendering
645SSR with Loaders: Next.js and Remix Patterns
646When Client Fetching is Actually Right
647The SEO and Performance Impact
648Migration Strategy: Moving Fetches Server-Side
649What 'Deriving State' Means
650The Symptom: Stale Derived Values
651Example: Filtering Props in an Effect
652Why It's Wrong: Double Rendering
653The Fix: Compute During Render
654When Computation is Expensive: useMemo
655Recognizing the Pattern in the Wild
656Exception: External System Synchronization
657Events vs Effects: The Fundamental Distinction
658The 'Handle Event in Effect' Antipattern
659Moving onClick Logic Out of Effects
660Form Submission: Event Handler, Not Effect
661The 'Derived Trigger' Problem
662Refactoring: From Effect to Direct Call

← React

Lesson 656 of 2,396·17. Common useEffect MistakesPro lesson

Exception: External System Synchronization

The rare valid case where useEffect is needed—syncing with non-React systems, not deriving from React values.

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