Template engine (like smarty) executed in web browser.

Example - HTML code:

<div id='x'>
{message}
<b>{+ 2 3}</b>
</div>
<script type='text/javascript'>
var t = new Template();
t.assign( new TemplateVar('message','Hello World!') );
var el = document.getElementById('x');
el.innerHTML = t.fetch( el.innerHTML );
</script>

Browser result:

<div id='x'>
Hello World!
<b>5</b>
</div>