How do I compile jade on request rather than just server start?

I'm looking to compile my jade on server request/response that way I can make changes to the jade file and see it in real time, rather than having to restart the server every time. This is the fake mockup I have so far.

var http = require('http')
  , jade = require('jade')
  , path = __dirname + '/index.jade'
  , str  = require('fs').readFileSync(path, 'utf8');


    function onRequest(req, res) {
        req({
            var fn   = jade.compile(str, { filename: path, pretty: true});
        });
        res.writeHead(200, {
            "Content-Type": "text/html"
        });

        res.write(fn());
        res.end();
    }

http.createServer(onRequest).listen(4000);
console.log('Server started.');

I hope I made myself clear!

You're only reading the file once, on server startup. If you wanted to have it read changes you'd have to read it on request, meaning your mock-up would look more like:

function onRequest(req, res) {
    res.writeHead(200, {
        "Content-Type": "text/html"
    });

    fs.readFile(path, 'utf8', function (err, str) {
        var fn = jade.compile(str, { filename: path, pretty: true});
        res.write(fn());
        res.end();
    });
}

Something like that would read the file every time, which is probably okay for development purposes, but if you only wanted to reload/process the file when something changed, you might use a file watcher (fs.watch might fit this bill).

Something like this (just an untested example as an idea):

var fn;

// Clear the fn when the file is changed
// (I don't have much experience with `watch`, so you might want to 
// respond differently depending on the event triggered)
fs.watch(path, function (event) {
    fn = null;
});

function onRequest(req, res) {
    res.writeHead(200, {
        "Content-Type": "text/html"
    });

    var end = function (tmpl) {
      res.write(tmpl());
      res.end();
    };

    if (fn) return end(fn);

    fs.readFile(path, 'utf8', function (err, str) {
        fn = jade.compile(str, { filename: path, pretty: true});
        end(fn);
    });
}