Calling Express Route internally from inside NodeJS

The 'usual' or 'correct' way to handle this would be to have the function you want to call broken out by itself, detached from any route definitions. Perhaps in its own module, but not necessarily. Then just call it wherever you need it. Like so:

function updateSomething(thing) {
    return myDb.save(thing);
}

// elsewhere:
router.put('/api/update/something/:withParam', function(req, res) {
    updateSomething(req.params.withParam)
    .then(function() { res.send(200, 'ok'); });
});

// another place:
function someOtherFunction() {
    // other code...
    updateSomething(...);
    // ..
}

This is an easy way to do an internal redirect in Express 4:

The function that magic can do is: app._router.handle()

Testing: We make a request to home "/" and redirect it to otherPath "/other/path"

var app = express()

function otherPath(req, res, next) {
  return res.send('ok')
}

function home(req, res, next) {
  req.url = '/other/path'
  /* Uncomment the next line if you want to change the method */
  // req.method = 'POST'
  return app._router.handle(req, res, next)
}

app.get('/other/path', otherPath)
app.get('/', home)