link.js

function keyToRegExp(key) {
  return new RegExp(':(' + key + ')(?:\\(([^\\(]+)\\))?');
}

function link(url, params) {
  return Object.keys(params).reduce(function (url, key) {
    url = url.replace(keyToRegExp(key), params[key]);
    return url;
  }, url);
}

module.exports = link;

routes.json

{
  "profile": "/user/:id(\\d+)",
  "profileComment": "/user/:id(\\d+)/comments/:commentId(\\d+)"
}

test.js

var routes = require('routes');
var link = require('link');

link(routes.profile, { id: 123 }); // /user/123
link(routes.profileComment, { id: 123, commentId: 321 }) // /user/123/comments/321