JSFiddle - React, Tailwind, and code Playground

HTML

<textarea cols="40" rows="10">Hello<div class="author"><br /><i> Written By <a href="http://localhost/user/admin">admin</a> </i></div></textarea>

JavaScript

$('textarea').each(function(index, element) {
   var textarea = $(element);
   textarea.val(textarea.val().replace(/<div class="author">.*?<\/div>/, ' Insert this'));
});