Using Q promises - is there a way to make this code less repetitive?

Q.ninvoke(mongoose,'connect', MONGODB_URL) .then(function () {    console.log('Wiping database...');    return Q.ninvoke(mongoose.connection.db, 'dropDatabase'); }) .then(function () {    console.log('Setting up test user...')    return Q.ninvoke(User, 'createUser', {        email: 'test@example.com',        password: 'tester'    }); }) .then(function (user) {    console.log('Finished.');    process.exit(); }) .catch(function(err) {    console.log(err); });

You can possibly shorten it with reusable oncomplete helper like this:

function oncomplete(deferred) {    return function (err, result) {        if (err) deferred.reject(new Error(err));        else deferred.resolve(result);    }}Q.fcall(function () {    var deferred = Q.defer();    console.log('Connecting to database:', MONGODB_URL, '...');    mongoose.connect(MONGODB_URL, oncomplete(deferred));    return deferred.promise;}).then(function () {    var deferred = Q.defer();    console.log('Wiping database...');    mongoose.connection.db.dropDatabase(oncomplete(deferred));    return deferred.promise;}).then(function () {    var deferred = Q.defer();    console.log('Setting up test user...');    User.createUser({        email: 'test@example.com',        password: 'tester'    }, oncomplete(deferred));    return deferred.promise;}).done(function () {    console.log('Finished.');    process.exit();}, function (err) {    console.error('An error occurred:', err.stack);});

If you're brave enough, you can drastically simplify it with Node v0.11 beta and yield keyword. That would implement an asynchronous state machine, so you could have pseudo-liner code flow without explicit callbacks.

Check out the async module, specifically waterfall. You can read about it here:

https://github.com/caolan/async#waterfalltasks-callback

Basically it allows you to chain a set of nested callbacks in a nice and concise manner.