Handlebars:
Template
{{! This comment will not show up in the output}}
<!-- This comment will show up as HTML-comment -->
{{!-- This comment may contain mustaches like }} --}}
Preparation-Script
// Handlebars.registerHelper('loud', function(string) {
//    return string.toUpperCase()
// });
Input
{}
Output
<!-- This comment will show up as HTML-comment -->
Last Updated: 10/18/2019, 10:48:38 AM