template.js.hb

Hello {{firstName|upper}} {{lastName|lower}} your encoded password is {{password|encode}}!

μMustache.js

var fs = require('fs');

var functions = {
	upper:  function (str) { return str.toUpperCase(); },
	lower:  function (str) { return str.toLowerCase(); },
	encode: function (str) { return str.replace(/(.)/g, '*'); }
};

var extractFunctions = function (group) {
	var filters = group.split("|");

	if (filters.length == 1) {
		return filters;
	}
	var value = filters.splice(0, 1);

	return filters.reduce(function(fnx, f) {
		functions[f] !== undefined ? fnx.push(functions[f]) : void 0;
		return fnx;
	}, [value]);
};


module.exports = {

	render: function(templateFile, data) {
		 
		return fs.readFileSync(templateFile, 'utf8').replace(

			/\{\{([^{}]*)\}\}/g,
			
			function (match, group) {

				var expandedGroup = extractFunctions(group),
				    group = expandedGroup.splice(0, 1);

				if (typeof data[group] !== 'undefined') {
					return expandedGroup.reduce(function(calculatedValue, f) {
						calculatedValue = f(calculatedValue);

						return calculatedValue;
					}, data[group]);
				};

				return '';
			}
		);
	}
}

console.log(
	module.exports.render("template.js.hb", {firstName: 'Simone', lastName: 'Di Maulo', password: 'password'})
);