template.js

var mtemplate = function(template, data){
        function replaceFn(match, prop){
            return (prop in data)? data[prop] : '';
        }
        return template.replace(/\{\{(\w+)\}\}/g, replaceFn);
    };

var output = mtemplate('{{foo}} / {{bar}}', {foo : 'prueba foo', bar: 'prueba bar'});

window.console.info(output);