title: How to solve react webpack problem with npm-start
body: <p>Here is my error page:</p>
  
  <blockquote>
    <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": "4.19.1"</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:\Users\Acer\node_modules\webpack (version: 4.28.3)</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>To fix the dependency tree, try following the steps below in the exact
    order:</p>
    
    <ol>
    <li>Delete package-lock.json (not package.json!) and/or yarn.lock in your project folder.</li>
    <li>Delete node_modules in your project folder.</li>
    <li>Remove "webpack" from dependencies and/or devDependencies in the package.json file in your project folder.</li>
    <li>Run npm install or yarn, depending on the package manager you use.</li>
    </ol>
    
    <p>In most cases, this should be enough to fix the problem. If this has
    not helped, there are a few other things you can try:</p>
    
    <ol start="5">
    <li><p>If you used npm, install yarn (<a href="http://yarnpkg.com/" rel="noreferrer">http://yarnpkg.com/</a>) and repeat the above steps with it instead.
     This may help because npm has known issues with package hoisting which may get resolved in future versions.</p></li>
    <li><p>Check if C:\Users\Acer\node_modules\webpack is outside your project directory.
     For example, you might have accidentally installed something in your home folder.</p></li>
    <li><p>Try running npm ls webpack in your project folder.
     This will tell you which other package (apart from the expected react-scripts) installed webpack.</p></li>
    </ol>
    
    <p>If nothing else helps, add SKIP_PREFLIGHT_CHECK=true to an .env file
    in your project. That would permanently disable this preflight check
    in case you want to proceed anyway.</p>
    
    <p>P.S. We know this message is long but please read the steps above :-)
    We hope you find them helpful!</p>
  
  <pre><code>npm ERR! code ELIFECYCLE
  npm ERR! errno 1
  npm ERR! first-app@0.1.0 start: `react-scripts start`
  npm ERR! Exit status 1
  npm ERR!
  npm ERR! Failed at the first-app@0.1.0 start script.
  npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
  
  npm ERR! A complete log of this run can be found in:
  npm ERR!     C:\Users\Acer\AppData\Roaming\npm-cache\_logs\2019-01-03T12_30_23_160Z-debug.log
  </code></pre>
  </blockquote>
  
  <p>I've applied all steps but, npm start command still doesn't work.
  What should I do?</p>