co Generator based control flow goodness for nodejs and the browser, using promises, letting you write non-blocking code in a nice-ish way. Co v4 co@4.0.0 has been released, which now relies on promises. It is a stepping stone towards ES7 async/await. The primary API change is how co() is invoked. Before, co returned a "thunk", which you then called with a callback and optional arguments. Now, co(