JSFiddle - React, Tailwind, and code Playground
HTML
<div id="div1"></div>
<div id="div2"></div>
<div id="div3"></div>
<div id="div4"></div>
CSS
div{
width:100px;
height:100px;
float:left;
background-color:#F00;
margin:10px;
}
JavaScript
$(document).ready(function() {
$('#div1,#div2,#div3,#div4').mouseover(function() {
$(this).css('opacity', .4).fadeTo(2000, 1.0);
}).mouseout(function() {
$(this).fadeTo(2000, 0.4);
});
});