title: Why does react slingshot repo uses both, Npm and yarn?
body: <p>I was taking a look at the react slingshot starter kit and I couldn't understand why the project uses npm and yarn at the same time. </p>
  
  <p>The repo's url is: <a href="https://github.com/coryhouse/react-slingshot" rel="nofollow noreferrer">https://github.com/coryhouse/react-slingshot</a></p>
  
  <p>Can someone give me an explanation about that?</p>
  
  <p>I heard that if you have yarn.lock (as the project does) you should use yarn. However all the command line commands are based on npm. Why?</p>