react-router-dom@4.0.0 requires a peer of react@^15 but none is installed. You must install peer dependencies yourself
You need React in your package.json
Try the following in the folder where your package.json is placed:
npm install react --saveIf react is already present in your package.json verify that the version is higher then 15.0.
If that's not fixing your error, please provide us your package.json
With the help of @rieckpil, I have followed following steps and it fixed my problem.
1: On this page I collected latest version for all following libraries react, react-dom, react-redux, react-router, react-router-dom, redux and replaced it in my package.json file.
2: Run npm install
3: Run npm start. If getting errors like above, simply restart you computer and run npm start again.