JSFiddle - React, Tailwind, and code Playground

HTML

<body>
<div id="x"></div>
<div id="y"></div>
</body>

CSS

body{
    margin: 0 0 0 0;
    width: 100%;
    height: 100%;
    padding: 0 0 0 0;
    background: #0f0;
}

#x{
    height: 100px;
    width: 100px;
    background: #f00;
}

#y{
    height: 100px;
    width: 100px;
    background: #00f;
}

#y:hover body{
    background: #f0f;
}

JavaScript

$('#y').hover(function(){
    $('body').css('background', '#f0f');
},function(){
    $('body').css('background', '');
});