JSFiddle - React, Tailwind, and code Playground

HTML

<div class="input-group-btn">
    
    <button class="btn" data-toggle="collapse">
        <span class="current" data-url="">Submenu1</span> <span class="right">&nabla;</span>
    </button>
    
    <ul id="categories" class="dropdown-menu">
        <li><a href="#" class="unicode ieUnicode">Submenu2</a></li>
        <li><a href="#" class="unicode ieUnicode">Submenu3</a></li>
        <li><a href="#" class="unicode ieUnicode">Submenu4</a></li>
        <li><a href="#" class="unicode ieUnicode">Submenu5</a></li>
        <li><a href="#" class="unicode ieUnicode">Submenu6</a></li>
    </ul>
    
</div>

CSS

.input-group-btn{
    position:relative;
}
.btn{
    width:300px;
    background-color:#ddd;
    color:red;
    border:1px solid #ccc;
    padding:10px;
    font-size:20px;
    text-align:left;
    cursor:pointer;
}
.btn .right{
    color:#fff;
    background-color:#000;
    border-radius:50%;
    display:inline-block;
    padding:0 5px;
    float:right;
}
.dropdown-menu{
   background-color: #ddd;
    border: 1px solid #ccc;
    list-style: none outside none;
    padding: 0;
    position: absolute;
    top: 34px;
    width: 300px;
    display:block;
    display:none;
    
}
.dropdown-menu li{
    border-bottom:1px solid #ccc;
    padding:10px;
    cursor:pointer;
}
.dropdown-menu li a{
    text-decoration:none;
    color:red;
    
}
.dropdown-menu li:hover,
.btn:hover {
    background-color:green;
    color#fff;
}
.dropdown-menu li:hover a{
    color:white;
}
.input-group-btn.open .dropdown-menu{
    display:block;
}
.dropdown-menu .right{
    color:#fff;
    background-color:#000;
    border-radius:50%;
    display:inline-block;
    padding:0 5px;
    float:right;
}

JavaScript

$('.btn').click(function(){
    $(this).parent().toggleClass('open');   //how use li appendto btn and dropdown-menu is hide
});

$('.dropdown-menu li').click(function(){
    $(this).closest('.dropdown-menu').find('.right').remove();
    $(this).append('<span class="right">&nabla;</span>')
});