title: Nextjs: Build optimization failed: found page without a React Component as default export
body: <p>I run this command:</p>
  <pre><code>npm run build
  </code></pre>
  <p>And I get this error:</p>
  <pre><code>&gt; Build optimization failed: found page without a React Component as default export in 
  pages/library/store
  </code></pre>
  <p>And this is my <code>store.tsx</code>:</p>
  <pre><code>const store = new Map&lt;string, any&gt;();
  export default store;
  </code></pre>
  <p>How can I fix it?</p>