JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-2.1.4.min.js"></script>
<span class="generate-email" data-part1="john" data-part2="gmail" data-part3="com">placeholder</span>

JavaScript

$(function() {
	$('.generate-email').each(function() {
		var that = $(this);
    that.html(
      that.data('part1') + '@' + that.data('part2') + '.' + that.data('part3')
    );
  });  
});