Monkey Patching in Node.js (sekistner.com)

FYI - no need for underscore if you're only targeting node.js. You can use Array.isArray and routes.map instead of _.isArray and _.map

> server.route = new Hapi.Server().route;

Seems wasteful to create an instance only to get a property, when you can just use `Hapi.Server.prototype.route` instead

Express offers something similar to organize/simplify your routing:

    var express = require('express');
    var appRoot = express();
    var appFoobar = express();
    appFoobar.get('/bar', function (req, res) { res.end('/foo/bar'); });

    appRoot.use('/foo', appFoobar);
    appRoot.listen(process.env.PORT);

    $ curl localhost:3000/foo/bar
    /foo/bar
    $

As for "monkey patching", overwriting methods is often a bad idea. It may be better to use a new method to call upon the old one:

    Hapi.Server.prototype.routeAPI = function (routes) {
     if (!Array.isArray(routes)) routes = [ routes ];
     routes = routes.map(function (route) {
       route.path = '/api' + route.path;
       return route;
     });
     return this.route(routes);
    }

Like nadadiv said, you could even have gone without recreating a Server() instance each time.