(Bootstrap 4)滚动到标签顶部-带有粘滞导航的窗格

<nav class="navbar navbar-expand-lg navbar-dark bg-dark fixed-top">
  <a class="navbar-brand" href="#">Logo</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>
  <div class="collapse navbar-collapse" id="navbarNav">
    <ul class="navbar-nav">
      <li class="nav-item active">
        <a class="nav-link" href="#section1">Section 1</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#section2">Section 2</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#section3">Section 3</a>
      </li>
    </ul>
  </div>
</nav>

<div id="section1" class="section">
  <h2>Section 1</h2>
  <p>Content of section 1</p>
</div>

<div id="section2" class="section">
  <h2>Section 2</h2>
  <p>Content of section 2</p>
</div>

<div id="section3" class="section">
  <h2>Section 3</h2>
  <p>Content of section 3</p>
</div>

$('body').scrollspy({ target: '.navbar', offset: 50 });