Here you will find the necessary solution and the required code:
How to insert an <em> tag when exceeding the 140 limit, i.e. negative?
... and here:
REGEX - Highlight more than 19 characters
Your question seems two-faced.
Note. I did not have the opportunity to post the above links as a comment (i.e. reputation-dependent privileges).
(. ):
HTML:
<!DOCTYPE html>
<html>
<head>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.1/jquery.min.js"></script>
<meta charset=utf-8 />
<title>JS Bin</title>
</head>
<body>
<h3>Your text here</h3>
<div contenteditable="true" id="myDiv">edit me
</div>
<p>
<h3>Stuff over 19 characters</h3>
<div id="extra">
</div>
<p>
<h3>Sample output</h3>
<div id="sample">
</div>
</body>
</html>
CSS
.highlight {
color:red;
}
JavaScript:
$(document).ready(function() {
$('#myDiv').keyup(function() {
var content = $('#myDiv').html();
var extra = content.match(/.{19}(.*)/)[1];
$('#extra').html(extra);
var newContent = content.replace(extra, "<span class='highlight'>" + extra + "</span>");
$('#sample').html(newContent);
});
});