React Modernization

Upgrade React applications from class components to hooks, adopt concurrent features, and migrate between major versions.

WHAT

Systematic patterns for modernizing React codebases:

• Class-to-hooks migration with lifecycle method mappings
• React 18/19 concurrent features adoption
• TypeScript migration for React components
• Automated codemods for bulk refactoring
• Performance optimization with modern APIs

WHEN

• Migrating class components to functional components with hooks
• Upgrading React 16/17 apps to React 18/19
• Adopting concurrent features (Suspense, transitions, use)
• Converting HOCs and render props to custom hooks
• Adding TypeScript to React projects

KEYWORDS

react upgrade, class to hooks, useEffect, useState, react 18, react 19, concurrent, suspense, transition, codemod, migrate, modernize, functional component

Installation

OpenClaw / Moltbot / Clawbot

npx clawhub@latest install react-modernization

Version Upgrade Paths

React 17 → 18 Breaking Changes

React 18 → 19 Breaking Changes

Class to Hooks Migration

Lifecycle Method Mappings

// componentDidMount → useEffect with empty deps
useEffect(() => {
  fetchData()
}, [])

// componentDidUpdate → useEffect with deps
useEffect(() => {
  updateWhenIdChanges()
}, [id])

// componentWillUnmount → useEffect cleanup
useEffect(() => {
  const subscription = subscribe()
  return () => subscription.unsubscribe()
}, [])

// shouldComponentUpdate → React.memo
const Component = React.memo(({ data }) => <div>{data}</div>)

// getDerivedStateFromProps → useMemo
const derivedValue = useMemo(() => computeFrom(props), [props])

State Migration Pattern