JSFiddle - React, Tailwind, and code Playground

HTML

<nav class="navbar">
  <ul class="navbar-nav">
    <li><a href="#">Home</a></li>
    <li><a href="#">About</a></li>
    <li class="dropdown"><a href="#">Contact &#9660;</a></li>
  </ul>

  <div class="big-dropdown">
    <a href="#">Link 1</a>
    <a href="#">Link 2</a>
    <a href="#">Link 3</a>
  </div>
</nav>

<div id="content">
  <p>
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    IpsumLorem IpsumLorem IpsumLorem IpsumLorem IpsumLorem IpsumLorem IpsumLorem IpsumLorem IpsumLorem IpsumLorem...

CSS

.navbar {
  position: fixed;
  width: 100%;
  background-color: #ebebeb;
  height: 4em;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  
}

.navbar-nav {
  display: flex;
  margin-right: 1em;

}

.navbar-nav > li > a {
  margin: 0 0.5em;
  text-decoration: none;
}

.big-dropdown {
  opacity: 0;
  height: 200px;
  background-color: #fff;
  position: absolute;
  left: -9999px; /* adjustment */
  top: 0;
  margin-top: 4em;
  width: 100%;

}

#content {
  position: relative;
  z-index: -1;
}

.show {
  opacity: 1!important;
  left: 0; /* new */
}

JavaScript

$('.navbar .dropdown').on('click', function() {
  $('.big-dropdown').toggleClass('show');
});