What is React component lifecycle?

Question

Accepted Answer

**Functional component lifecycle:**

```tsx
function Component() {
  useEffect(() => {
    // componentDidMount + componentDidUpdate
    console.log("mounted or updated");
    return () => {
      // componentWillUnmount
      console.log("cleanup");
    };
  }, [dependency]);
}
```

**Hooks mapping:**
- useState: state
- useEffect: side effects (mount/update/unmount)
- useLayoutEffect: DOM mutations
- useRef: instance values
- useMemo: memoized computation
- useCallback: memoized functions

**No class component lifecycle:** No componentDidMount, componentDidUpdate, componentWillUnmount — all via hooks now.

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