title: Export module via Webpack
body: <p>I am working on a React app. In <code>index.js</code> am exporting some variables, e.g.</p>
  
  <pre><code>export const a="Hello";
  export const b=[1,2,3];
  </code></pre>
  
  <p>In webpack.config.js:</p>
  
  <pre><code>...
  output: {
   ...
   library: "myApp",
   libraryTarget: "window"
  },
  ...
  </code></pre>
  
  <p>I know <code>window.myApp</code> is now a <code>module</code> which includes all the exported variables from <code>index.js</code>. What I do not know is how the above works. How this module is being created and why it includes only the exports from index.js and not other files as well? How, may I include exports from another specific file? </p>