JSFiddle - React, Tailwind, and code Playground

HTML

<div class="btn-group">
    <a class="btn dropdown-toggle" data-toggle="dropdown" href="#">
        <font id="dropdownMenu" >inch</font>
        <span class="caret"></span>
    </a>
    <ul id="dropdownList" class="dropdown-menu">
        <li><a href="#">inch</a></li>
        <li><a href="#">cm</a></li>
        <li><a href="#">mm</a></li>
    </ul>
</div>

JavaScript

$('#dropdownList li').click(function () {
    console.log($(this).text());
    document.getElementById('dropdownMenu').innerHTML = $(this).text();
});