Infinite Loop Caused by Missing Dependency

1. Missing dependency array (effect runs every render)
2. Empty dependency array but accessing changing state
3. Object/array in dependencies causing it to always change
4. Function called in effect that updates state
5. Not understanding closure and stale values

Always include dependency array:

// Bad - no deps, runs every render
useEffect(() => {
  fetchData(); // calls API every render
});

// Good - runs once on mount
useEffect(() => {
  fetchData();
}, []);

// Good - runs when id changes
useEffect(() => {
  fetchData(id);
}, [id]);

Use ESLint plugin to catch missing dependencies.