goosestream.js

// today
Thing.find({ name: {$in: someNames }}).each(function (err, doc, next) {
  if (err) return done(err);
  if (!doc) return done();

  doSomethingAsync(doc, function (err) {
    if (err) return done(err);
    // we are handling iteration manually by using `next`
    next();
  });
});

// tomorrow
var cursor = Thing.find({ name: {$in: someNames }}).cursor();
cursor.on('end', done);   // the cursor is now closed - no memory leaks
cursor.on('error', done); // the cursor is now closed - no memory leaks

cursor.on('doc', function (doc, next) {
  var self = this;
  doSomethingAsync(doc, function (err) {
    if (err) return self.emit('error', err);
    // `next` is still optional, if not passed then auto iteration
    // would take place the same as today.
    next();
  });
});

// or

cursor.on('doc', function (doc) {
  // i decide that i'm finished with this cursor.
  this.close();
  // no more doc events fire.
  // underlying cursor is closes - memory cleaned up
  // this fires `end` event
  // TODO do we need to fire `close`?
});