title: Add external libraries in Angular 8
body: <p>I want to use some external jQuery libraries in my Angular project.</p>
  
  <p>I added these libraries inside <code>index.html</code> file, but they are not working. I also added my <code>.js</code> files in <code>angular.json</code>, but the problem still exists. I add libraries like this:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>&lt;!-- CUSTOM JS --&gt;
  &lt;script src="assets/js/jquery.app.js"&gt;&lt;/script&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>Actually the code in this js file is not reachable. It seems Angular does not understand it to go and run that specific function in this file.</p>
  
  <p>I expect a menu item shows its sub menus but the jQuery code does not work in Angular.</p>