templating.js

(function (value, config) { 
    var matchbox = /{([^a-z]?)([a-z_]+)([^a-z|]?)(\|[^}]+)?}/g;
    var translator = function (match, prefix, value, suffix, defaultValue) {
        if (config.hasOwnProperty(value)) {
            return prefix + config[value] + suffix;
        }

        if (defaultValue) {
            return defaultValue.replace('|', '');
        }

        return '';
    };

    return value.replace(matchbox, translator);
}('server { listen {port|80}; server_name {sub_domain.}{domain}; }', {
    // port: 8080,
    sub_domain: 'www',
    domain: 'example.com'
}));

// "server { listen 80; server_name www.example.com; }"