JSFiddle - React, Tailwind, and code Playground

HTML

<div class="a">
    <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque alias repellendus fugiat maxime reiciendis sunt corrupti ratione beatae amet odio.</p>
</div>
<div class="b">
    <ul>
        <li><a href = "#">link 1</a></li>
        <li><a href = "#">link 1</a></li>
        <li><a href = "#">link 1</a></li>
    </ul>
</div>

CSS

div{
    float:left;
    clear:both;
    width:500px;
    height:100px;
    margin:10px
}
div.a{
    background:#ff5555;
    
}
div.b{
    background:#5555ff;
}

JavaScript

var diva = $('div.a'),
    divb = $('div.b')
divb.hide();
diva.on('mouseover', function(){
    divb.show();
});
diva.on('mouseout', function(){
    divb.hide();
});