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/1.8.2/themes/ui-lightness/jquery-ui.css">
<div id="bigchuck">
    <p>blah blah blah.</p>
    <p>yada yada yada.</p>
    <p>Tada. Bing bong the witch is dead. Door bell.</p>
</div>

CSS

span {
    color: red;
}

JavaScript

$('#bigchuck p:last').html( function(i,html) {
  var arr = html.split(". ");
  arr[arr.length-1]="<span>"+arr[arr.length-1]+"</span>";
  return arr.join(". ");
});

alert($('#bigchuck p:last').html())