title: How to change the default port in react js
body: <p>I could able to start react js with default port 3000. But, when I customised the port to 4200, <code>"start": "PORT=4200 react-scripts start"</code>(Just changed in the package.json), I am not able to start the react js application.</p>
  
  <pre><code>'PORT' is not recognized as an internal or external command,
  operable program or batch file.
  npm ERR! code ELIFECYCLE
  npm ERR! errno 1
  npm ERR! todo-app@0.1.0 start: `PORT=4200 react-scripts start`
  npm ERR! Exit status 1
  npm ERR!
  npm ERR! Failed at the todo-app@0.1.0 start script.
  npm ERR! This is probably not a problem with npm. There is likely additional lo
  ging output above.
  
  npm ERR! A complete log of this run can be found in:
  </code></pre>