JSFiddle - React, Tailwind, and code Playground

HTML

<!-- exemplo retirado de http://www.itworld.com/article/2832973/development/setting-an-active-menu-item-based-on-the-current-url-with-jquery.html -->
<header>
    <ul class="nav">
        <li><a href="pagina.html">Home</a>
        </li>
        <li>|</li>
        <li><a href="pagina2.html">Pagina</a>
        </li>
        <li>|</li>
        <li><a href="pagina3.html">Sobre</a>
        </li>
        <li>|</li>
        <li><a href="pagina4.html">Contato</a>
        </li>
    </ul>
</header>

CSS

a {
    color:#000;
    text-decoration:none;
}
a:hover {
    text-decoration:underline;
}
a:visited {
    color:#000;
}
.nav {
    padding:10px;
    border:solid 1px #c0c0c0;
    border-radius:5px;
    float:left;
}
.nav li {
    list-style-type:none;
    float:left;
    margin:0 10px;
}
.nav li a {
    text-align:center;
    width:55px;
    float:left;
}
.nav li.active {
    background-color:green;
}
.nav li.active a {
    color:#fff;
    font-weight:bold;
}

JavaScript

/**
O autor deste codigo Ă© Matthew Mombrea 
*/
$(function () {
    var path = window.location.pathname;
    path = path.replace(/\/$/, "");
    path = decodeURIComponent(path);

    $(".nav a").each(function () {
        var href = $(this).attr('href');
        if (path.substring(0, href.length) === href) {
            $(this).closest('li').addClass('active');
        }
    });
});