Need I install react-router if I installed @types/react-router?

Question

I started a react project through create-react-app

create-react-app my-app --scripts-version=react-scripts-ts

And I got the following package.json

{
  "name": "my-app",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "react": "^16.4.1",
    "react-dom": "^16.4.1",
    "react-scripts-ts": "2.16.0"
  },
  "scripts": {
    "start": "react-scripts-ts start",
    "build": "react-scripts-ts build",
    "test": "react-scripts-ts test --env=jsdom",
    "eject": "react-scripts-ts eject"
  },
  "devDependencies": {
    "@types/jest": "^23.1.0",
    "@types/node": "^10.3.3",
    "@types/react": "^16.3.18",
    "@types/react-dom": "^16.0.6",
    "typescript": "^2.9.2"
  }
}

I understand that packages in devDependencies won't be needed for building the production bundle, therefore we have dependencies and devDependencies separately. However, if I want to add a new package, such as react-router, should I do the following two separately like following?

npm install --save react-router
npm install --save-dev @types/react-router

or should I do

npm install --save @types/react-router

If either way if fine, what's the difference between the two approaches?

Answer 1

npm install --save react-router Installs the actual module while,
npm install --save-dev @types/react-router only install type information for typescript. The type information has no functionality of its own, so you need to install both.
The type information is installed as a dev dependency because it isn't required after the build process which transforms typescript into JavaScript.

Answer 2

The answer to the question is yes.

Installing @types/react-router you only get TypeScript type definitions for react-router and not the react-router functionality.