Comparison

At this point of the chapter, we should have a better understanding of what options we have to tame the asynchronous nature of Node.js. Each one of the solutions presented has its own pros and cons. Let's summarize them in the following table:

Solutions	Pros	Cons
Plain JavaScript	Does not require any additional library or technology Offers the best performances Provides the best level of compatibility with third-party libraries Allows the creation of ad hoc and more advanced algorithms	Might require extra code and relatively complex algorithms
Async	Simplifies the most common control flow patterns Is still a callback-based solution Good performances	Introduces an external dependency Might still not be enough for advanced flows
Promises	Greatly simplify the most common control flow patterns Robust error handling Part of the ES6 specification Guarantee deferred invocation of onFulfilled and onRejected	Might require an external dependency Require to promisify callback-based APIs Only a few third-party libraries support promises natively Introduce a small performance hit
Generators	Make nonblocking API look like blocking Simplify error handling Part of ES6 specification	Require a complementary control flow library Still require callbacks or promises to implement nonsequential flows Not yet available by default on Node.js Require to thunkify or promisify nongenerator-based APIs

Note

It is worth mentioning that we chose to present in this chapter only the most popular solutions to handle asynchronous control flow, or the ones receiving a lot of momentum, but it's good to know that there are a few more options you might want to look at, for example, Fibers (https://npmjs.org/package/fibers) and Streamline (https://npmjs.org/package/streamline).