JSFiddle - React, Tailwind, and code Playground

HTML

<button>Hover</button>

CSS

body{-webkit-transition:1s;}

button{border:none; background:#0f3361; margin:10px; color:#fff;
  padding:10px 20px; -webkit-transition:0.4s; font-weight:bold;
  cursor:pointer;}
button:hover{background:#315e99;}

JavaScript

$(document).ready(function(){
  $('button').hover(function() {
    $('body').css('background','#525252');
  }, function() {
    $('body').css('background','#fff');
  });
});