JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<h1>Smooth Accordion Dropdown Menu Demo</h1>
<!-- Contenedor -->
<ul id="accordion" class="accordion effect7">
  <li>
    <div class="link"><i ></i>Group 1<i class="fa fa-chevron-down"></i></div>
    <ul class="submenu">
      <li><a href="#">Value 1</a></li>
      <li><a href="#">Value 2</a></li>
      <li><a href="#">Value 3</a></li>
      <li><a href="#">Value 4</a></li>
    </ul>
  </li>
  <li>
    <div class="link"><i class=""></i>Group 2<i class="fa fa-chevron-down"></i></div>
    <ul class="submenu">
      <li><a href="#">Value 1</a></li>
      <li><a href="#">Value 2</a></li>
      <li><a href="#">Value 3</a></li>
    </ul>
  </li>
  <li>
    <div class="link"><i class=""></i>Group 3<i class="fa fa-chevron-down"></i></div>
    <ul class="submenu">
      <li><a href="#">Value 1</a></li>
    </ul>
  </li>
  <li>
    <div class="link"><i class=""></i>Group 4<i class="fa fa-chevron-down"></i></div>
    <ul class="submenu">
      <li><a href="#">Value 1</a></li>
      <li><a href="#">Value 2</a></li>
      <li><a href="#">Value 3</a></li>
    </ul>
  </li>  
  <li>
    <div class="link"><i class=""></i>Group 5<i class="fa fa-chevron-down"></i></div>
    <ul class="submenu">
      <li><a href="#">Value 1</a></li>
      <li><a href="#">Value 2</a></li>
      <li><a href="#">Value 3</a></li>
    </ul>
  </li>
  <li>
    <div class="link"><i class=""></i>Group 6<notes></notes><i class="fa fa-chevron-down"></i></div>
    <ul class="submenu">
      <li><a href="#">Value 1</a></li>
    </ul>
  </li>
  <li>
    <div class="link"><i class=""></i>Group 7<i class="fa fa-chevron-down"></i></div>
    <ul class="submenu">
      <li><a href="#">Value 1</a></li>
    </ul>
  </li>
</ul>

CSS

* {
  margin: 0;
  padding: 0;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

body {
  background: url('https://2cdn.tutsplus.com/webdesign/authors/legacy/chris%20brown/2012/09/18/climpek.png') repeat;
  font-family: 'Open Sans', Arial, Helvetica, Sans-serif, Verdana, Tahoma;
}

ul { list-style-type: none; }

a {
  color: #b63b4d;
  text-decoration: none;
}

/** =======================
* Contenedor Principal
===========================*/


h1 {
  color: #FFF;
  font-size: 24px;
  font-weight: 400;
  text-align: center;
  margin-top: 80px;
}

h1 a {
  color: #c12c42;
  font-size: 16px;
}

.accordion {
  width: 100%;
  max-width: 360px;
  margin: 30px auto 20px;
  background: #fff;
  -webkit-border-radius: 4px;
  -moz-border-radius: 4px;
  border-radius: 4px;
}

.accordion .link {
  cursor: pointer;
  display: block;
  padding: 15px 15px 15px 42px;
  color: #000;
  font-size: 14px;
  font-weight: 700;
  border-bottom: 1px solid #CCC;
  position: relative;
  -webkit-transition: all 0.4s ease;
  -o-transition: all 0.4s ease;
  transition: all 0.4s ease;
}

.accordion li:last-child .link { border-bottom: 0; }

.accordion li i {
  position: absolute;
  top: 16px;
  left: 12px;
  font-size: 18px;
  color: #595959;
  -webkit-transition: all 0.4s ease;
  -o-transition: all 0.4s ease;
  transition: all 0.4s ease;
}

.accordion li i.fa-chevron-down {
  right: 12px;
  left: auto;
  font-size: 16px;
}

.accordion li.open .link { color: #061283; }

.accordion li.open i { color: #b63b4d; }

.accordion li.open i.fa-chevron-down {
  -webkit-transform: rotate(180deg);
  -ms-transform: rotate(180deg);
  -o-transform: rotate(180deg);
  transform: rotate(180deg);
}

/**
* Submenu
-----------------------------*/


.submenu {
  display: none;
  background: rgba(0, 0, 0, 0.6);
  font-size: 14px;
}

.submenu li { border-bottom: 1px solid #4b4a5e; }

.submenu a {
  display: block;
  text-decoration: none;
  color: #d9d9d9;
  padding: 12px;
 ...

JavaScript

function Accordion(el, multiple) {
  this.el = el || {};
  this.multiple = multiple || false;

  const links = this.el.find('.link');
  links.on('click', {
    el: this.el,
    multiple: this.multiple
  }, this.dropdown);
}

Accordion.prototype.dropdown = function(e) {
  const $el = e.data.el;
  const $this = $(this);
  const $next = $this.next();

  $next.slideToggle();
  $this.parent().toggleClass('open');

  if (!e.data.multiple) {
    $el.find('.submenu').not($next).slideUp().parent().removeClass('open');
  }
}	

const accordion = new Accordion($('#accordion'), false);
$('#accordion').find('.link:first').click();