title: "npm start" doesn't work on any react-js project
body: <p><a href="https://i.stack.imgur.com/Aof8g.png" rel="nofollow noreferrer">[package.json]</a>
  i tried everything i tried to update npm, node, webpack also. </p>
  
  <p>this is what i do: 
  <strong>npx create-react-app testapp</strong></p>
  
  <p><strong>cd testapp</strong></p>
  
  <p><strong>npm start or yarn start</strong></p>
  
  <p>give me this: </p>
  
  <p>OUTPUT:</p>
  
  <p>There might be a problem with the project dependency tree.
  It is likely not a bug in Create React App, but something you need to fix locally.</p>
  
  <p>The react-scripts package provided by Create React App requires a dependency:</p>
  
  <p>"webpack": "4.39.1"</p>
  
  <p>Don't try to install it manually: your package manager does it automatically.
  However, a different version of webpack was detected higher up in the tree:</p>
  
  <p>C:\node_modules\webpack (version: 4.38.0)</p>
  
  <p>Manually installing incompatible versions is known to cause hard-to-debug issues.</p>
  
  <p>If you would prefer to ignore this check, add SKIP_PREFLIGHT_CHECK=true to an .env file in your project.
  That will permanently disable this message but you might encounter other issues.</p>
  
  <p>npm ERR! errno 1
  npm ERR! client@0.1.0 start: <code>react-scripts start</code>
  npm ERR! Exit status 1
  npm ERR!
  npm ERR! Failed at the client@0.1.0 start script.
  npm ERR! This is probably not a problem with npm. There is likely additional logging output above.</p>
  
  <p>npm ERR! A complete log of this run can be found in:</p>