JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.microsoft.com/ajax/jquery.validate/1.7/jquery.validate.js"></script>
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/ui-lightness/jquery-ui.css">
<input id='UseUsername' type='checkbox' /> check me

<div id='div'>show or hide me</div>

CSS

div {
    width: 100px;
    height: 100px;
    border: 2px dashed orange;
    background: yellow;
    color: orange;
    display: none;
}

JavaScript

$('#UseUsername').change(function(){
    $('#div').toggle(this.checked); 
});