JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mainnav">
    <ol id="toc">
        <li id="first" class="current"><a href="#"><span>MainNav1</span></a>
            <div id="subnav1" class="subnav" style="display:none">
                <a class="bsub2" href="#">nav1</a>
                <div class="sub2">
                    <a class="sub2" href="#">subnav1</a>
                    <a class="sub2" href="#">subnav2</a>
                    <a class="sub2" href="#">subnav3</a>
                </div>
                <a class="bsub3" href="#">nav2</a>
                <div class="sub3">
                    <a class="sub2" href="#">Subnavigationspunkt 1</a>
                    <a class="sub2" href="#">Subnavigationspunkt 2</a>
                    <a class="sub2" href="#">Subnavigationspunkt 3</a>
                    <a class="sub2" href="#">Subnavigationspunkt 4</a>
                </div>
                <a href="#">navigation 4</a>
                <a href="#">Navigation 5</a>
            </div>
        </li>
        
        <li><a href="#"><span>MainNav2</span></a></li>
        <li><a href="#"><span>MainNav3</span></a></li>
    </ol>
</div>

CSS

div#mainnav ol#toc
{
    height: 2em;
    list-style: none;
    margin: 0;
    padding: 0;
}

div#mainnav ol#toc li
{
    float: left;
    margin: 0 1px 0 0;
}

div#mainnav ol#toc a
{
    background: #003399;
    color: #ffffff;
    display: block;
    float: left;
    height: 2em;
    padding-left: 10px;
    text-decoration: none;
    width: 128px;
}
div#mainnav ol#toc span
{
    background: url(/img/tabs.gif) 100% 0;
    display: block;
    line-height: 2em;
    padding-right: 10px;
    text-align: center;
    font-weight: 600;
}
div#mainnav ol#toc a:hover
{
    background-color: #3af;
    background-position: 0 -60px;
}

div#mainnav ol#toc a:hover span
{
    background-position: 100% -60px;
}

div#mainnav ol#toc li.current a
{
    background-color: #48f;
    background-position: 0 -60px;
    color: #fff;
    font-weight: bold;
}

div#mainnav ol#toc li.current span
{
    background-position: 100% -60px;
}

/* Subnav */

div#subnav1
{
    background: #E9F0F8;
    position: absolute;
    left: 0px;
    top: 32px;
    z-index: 1000;
    width: 200px;
    border-top: 10px solid #003399;
}
div.subnav a
{
    text-decoration: none !important;
    float: none !important;
    width: 175px !important;
    color: #003399 !important;
    height: 15px !important;
    font-size: 13px !important;
    font-weight: normal !important;
    display: block !important;
    background: url('/img/subnavbox_0.png') !important;
    border-bottom: 1px solid #ffffff !important;
    padding: 5px 5px 5px 20px !important;
}
div.subnav a.sub2
{
    background: url('/img/subnavbox_1.png') !important;
    padding: 5px 5px 5px 30px !important;
    width: 165px !important;
}
div.subnav a:hover
{
    background: url('/img/subnavbox_0_h.png') repeat-x !important;
    color: #ffffff !important;
}
div.subnav a.sub2:hover
{
    background: url('/img/subnavbox_1_h.png') repeat-x !important;
    color: #ffffff !important;
}

JavaScript

function nav()
    {
        $('div#subnav1').hide();
        $('div#subnav1 div.sub2').hide();
        $('div#subnav1 div.sub3').hide();
        $('div#mainnav ol li#first').mouseover(function()
        {
            $('div#subnav1').show("fade", {}, 500);
        });
        $('div#mainnav ol li#first').mouseleave(function()
        {
            $('div#subnav1 div.sub2').hide();
            $('div#subnav1 div.sub3').hide();
            $('div#subnav1').hide("fade", {}, 500);
        });
        $('div#subnav1 a.bsub2').mouseover(function()
        {
            $('div#subnav1 div.sub3').hide();
            $('div#subnav1 div.sub2').show("blind", {}, 500);
        });
        $('div#subnav1 div.sub2').mouseleave(function()
        {
            $('div#subnav1 div.sub2').hide("blind", {}, 500);
        });
        $('div#subnav1 a.bsub3').mouseover(function()
        {
            $('div#subnav1 div.sub2').hide();
            $('div#subnav1 div.sub3').show("blind", {}, 500);
        });
        $('div#subnav1 div.sub3').mouseleave(function()
        {
            $('div#subnav1 div.sub3').hide("blind", {}, 500);
        });
    };
$(document).ready(function(){
    nav();
    
});