JSFiddle - React, Tailwind, and code Playground

HTML

<div id="test">hover me please</div>

CSS

div {
    width: 250px;
    height: 60px;
    background-color: black;
    color: white;
}

JavaScript

$(document).ready(function(){
    $('#test').bind('mouseenter', function() {
    var self = $(this);
    this.iid = setInterval(function() {
       self.append('X');
    }, 525);
}).bind('mouseleave', function(){
    this.iid && clearInterval(this.iid);
});

});