Handlebars:
Template
<p>{{firstname}} {{lastname}}</p>
Preparation-Script
// Handlebars.registerHelper('loud', function(string) {
//    return string.toUpperCase()
// });
Input
{
  firstname: "Yehuda",
  lastname: "Katz",
}
Output
<p>Yehuda Katz</p>
Last Updated: 8/26/2019, 9:47:01 PM