Adding TypeScript to existing create-react-app app

If you want to add TypeScript to the existing react app use below command

npm install --save-dev typescript @types/node @types/react @types/react-dom @types/jest

Rename at least one file from js/jsx to .ts/tsx. For example, rename index.js to index.ts or index.tsx and then start the server. This will generate the tsconfig.json file automatically and you are ready to write React in TypeScript.

As of react-scripts 2.10 you can add TypeScript to an existing project or when creating a new project.

existing project

yarn add typescript @types/node @types/react @types/react-dom @types/jest --dev

...then rename your .js files to .tsx

new project

yarn create react-app my-app --template typescript

You can read more here.

There is a recent pull request adding Typescript. It's not merged yet.

Also, the next major version of CRA will upgrade to Babel 7, which supports Typescript.

So I'd suggest you to wait a few weeks. It should be really easy then to add TS to any CRA project.

You can add typescript to an existing project using one of the following commands:

To add TypeScript to an existing Create React App project, first install it:

npm install --save typescript @types/node @types/react @types/react-dom @types/jest

or

yarn add typescript @types/node @types/react @types/react-dom @types/jest

You can read more here

But the problem is when you are changing a file except index.js like App.js to App.tsx it gives you an error that module not found error can't resolve './App' . The source of this issue is lacking a tsconfig.json file. So by creating one the error would be removed. I recommend using the below tsconfig:

 {
  "compilerOptions": {
    "target": "es5",
    "lib": ["dom", "dom.iterable", "esnext"],
    "allowJs": true,
    "skipLibCheck": true,
    "esModuleInterop": true,
    "allowSyntheticDefaultImports": true,
    "strict": true,
    "module": "esnext",
    "moduleResolution": "node",
    "resolveJsonModule": true,
    "isolatedModules": true,
    "noEmit": true,
    "jsx": "react-jsx"
  },
  "include": ["src"],
  "exclude": [
    "node_modules"
  ]
}