<title>jQuery wrapInner()</title>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" />
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
div{font-size:16px;height:40px;line-height:30px;width:300px;background:#11a286;padding:5px;color:#FFF;margin:0 0 10px 0}
$(document).ready(function() {
$("#button").click(function() {
$("p").wrapInner('<em></em>');
<p>This is a paragraph.</p>
<button style="margin:0 0 10px 0;background:#e8e8e8;" class="btn" id="button">Click here to wrap emphasized element around the content of p element</button><br />