title: Bootstrap4 typings(index.d.ts) cannot find module 'popper.js' on VisualStudio 2019 with TypeScript3.9 and Libman
body: <p>I use VisualStudio 2019 with TypeScript3.9 and Libman.</p>
  <p>And I need Bootstrap4 and jQuery.
  So try get these libraries and typings(index.d.ts) by Libman.</p>
  <p>Then Bootstrap4 typing(index.d.ts) get error &quot;Cannot find module popper.js&quot;.</p>
  <pre class="lang-js prettyprint-override"><code>// Type definitions for Bootstrap 4.5
  // Project: https://github.com/twbs/bootstrap/, https://getbootstrap.com
  // Definitions by: denisname &lt;https://github.com/denisname&gt;
  //                 Piotr Błażejewicz &lt;https://github.com/peterblazejewicz&gt;
  // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
  // TypeScript Version: 2.3
  
  /// &lt;reference types=&quot;jquery&quot;/&gt;
  
  import * as Popper from &quot;popper.js&quot;;     // ERROR!: &quot;Cannot find module popper.js&quot;
  </code></pre>
  <hr />
  <p>I found similar problems and answers.</p>
  <ul>
  <li><a href="https://stackoverflow.com/questions/54893300/bootstrap-4-typescript-type-definition-fails-to-compile-cannot-find-module-po">Bootstrap 4 TypeScript Type Definition fails to compile - Cannot find module &#39;popper.js&#39;</a></li>
  <li><a href="https://stackoverflow.com/questions/48402380/cannot-find-module-popper-js-angular-5-visual-studio-2017-asp-net-core">Cannot find module &quot;popper.js&quot; Angular 5 Visual Studio 2017 asp.net core</a></li>
  <li><a href="https://stackoverflow.com/questions/52124273/angular-types-bootstrap-error-namespace-popper-js-has-no-exported-member">Angular @types/bootstrap error: Namespace &#39;popper.js&#39; has no exported member</a></li>
  </ul>
  <p>It could only solve the problem temporarily.</p>
  <p>I changed bootstrap4 typing(index.d.ts) to relative path as <code>import * as Popper from &quot;../popper_v1&quot;;</code> is fixed error.
  But Libman override this manually-changed index.d.ts.</p>
  <p>_</p>
  <p>What can I do to fix this error?
  Do I need to install manually modified index.d.ts, like Popper v1.X?</p>
  <p>Thanks.</p>
  <hr />
  <h3>Steps to reporduce error.</h3>
  <ol>
  <li><p>Create ASP.Net4 MVC Project on .Net Framework 4.8</p>
  </li>
  <li><p>Create libman.json to add some libraries and TS typings</p>
  </li>
  </ol>
  <pre><code>{
    &quot;version&quot;: &quot;1.0&quot;,
    &quot;defaultProvider&quot;: &quot;jsDelivr&quot;,
    &quot;libraries&quot;: [
      {
        &quot;library&quot;: &quot;bootstrap@4.5.2&quot;,
        &quot;destination&quot;: &quot;lib/bootstrap/&quot;
      },
      {
        &quot;library&quot;: &quot;@types/bootstrap@4.5.0&quot;,
        &quot;destination&quot;: &quot;lib/types/bootstrap/&quot;
      },
      {
        &quot;library&quot;: &quot;jquery@3.5.1&quot;,
        &quot;destination&quot;: &quot;lib/jquery/&quot;,
        &quot;files&quot;: [
          &quot;dist/jquery.js&quot;,
          &quot;dist/jquery.min.js&quot;,
          &quot;dist/jquery.min.map&quot;,
          &quot;dist/jquery.slim.js&quot;,
          &quot;dist/jquery.slim.min.js&quot;,
          &quot;dist/jquery.slim.min.map&quot;,
          &quot;external/sizzle/LICENSE.txt&quot;,
          &quot;external/sizzle/dist/sizzle.js&quot;,
          &quot;external/sizzle/dist/sizzle.min.js&quot;,
          &quot;external/sizzle/dist/sizzle.min.map&quot;,
          &quot;AUTHORS.txt&quot;,
          &quot;LICENSE.txt&quot;,
          &quot;README.md&quot;
        ]
      },
      {
        &quot;library&quot;: &quot;@types/jquery@3.5.1&quot;,
        &quot;destination&quot;: &quot;lib/types/jquery/&quot;
      },
      {
        &quot;library&quot;: &quot;@types/sizzle@2.3.2&quot;,
        &quot;destination&quot;: &quot;lib/types/sizzle/&quot;
      },
      {
        &quot;provider&quot;: &quot;cdnjs&quot;,
        &quot;library&quot;: &quot;popper.js@1.16.1&quot;,
        &quot;destination&quot;: &quot;lib/popper.js/&quot;
      },
      {
        &quot;provider&quot;: &quot;filesystem&quot;,
        &quot;library&quot;: &quot;lib_ManualInstallSources/popper_v1/&quot;,
        &quot;destination&quot;: &quot;lib/types/popper_v1/&quot;
      }
    ]
  }
  </code></pre>
  <p>** Note: I got typing(index.d.ts) of popper.js ver.1.X from GitHub repository.</p>
  <ol start="3">
  <li>Create tsconfig.json</li>
  </ol>
  <pre><code>{
    &quot;compilerOptions&quot;: {
      &quot;noImplicitAny&quot;: false,
      &quot;noEmitOnError&quot;: true,
      &quot;removeComments&quot;: false,
      &quot;sourceMap&quot;: true,
      &quot;target&quot;: &quot;es5&quot;,
      &quot;lib&quot;: [ &quot;ES6&quot;, &quot;DOM&quot; ],
      &quot;baseUrl&quot;: &quot;.&quot;,
      &quot;typeRoots&quot;: [
        &quot;./lib/types&quot;
      ]
    },
    &quot;exclude&quot;: [
      &quot;node_modules&quot;,
      &quot;wwwroot&quot;,
      &quot;lib&quot;
    ]
  }
  </code></pre>
  <p>After these steps, bootstrap4 typing(index.d.ts) get error &quot;Cannot find module popper.js&quot; on <code>import * as Popper from &quot;popper.js&quot;;</code>.</p>
  <hr />