If you want to add Typescript in your existing react app, this is a simple ways that you could do to make it happen. First install the typescript itself
npm install --save typescript @types/node @types/react @types/react-dom @types/jest
After that add the typescript config
npx tsc --init
Then update packgae.json
"build": "tsc",Also in tsconfig.js activate
"jsx": "preserve" After that activate or uncomment some more inside the typescript config
"rootDir": "src",
"outDir": "build", Update all .js extension file to .tsx. If Everything is done, to prevent any error in index.tsx add !
const root = ReactDOM.createRoot(document.getElementById('root')!);After you could try to run the app
npm start