JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://raw.github.com/wycats/handlebars.js/1.0.0/dist/handlebars.js"></script>
<script type='text/template' id='src'>
{{#ifor firstname lastname}}
<p>
  {{#if firstname}}
    <span class="firstname">{{firstname}}</span>
  {{/if}}

  {{#if lastname}}
    <span class="lastname">{{lastname}}</span>
  {{/if}}
</p>
{{else}}
    Nope
{{/ifor}}
</script>

CSS

p {background: green; color: white}

JavaScript

Handlebars.registerHelper('ifor', function() {
    var l, opts;

    opts = Array.prototype.pop.call(arguments);
    for (l = arguments.length-1; l>=0; l--) {
        //if (typeof(arguments[l])==='undefined')
        if (arguments[l])
            return opts.fn(this);
    }
    
    return opts.inverse(this);
});

var tpl = Handlebars.compile($('#src').html());
$('body').append(tpl({
    firstname: 'first'
}));
$('body').append(tpl({
   
}));
$('body').append(tpl({
    firstname: 'first',
    lastname: 'last'
}));