More and more JavaScript libraries and client-side frameworks use promises to manage asynchronous data. But now you’re just using a .then() method to pass the same handler functions you did before. What is so great about that? Promises are not just a different place to specify callbacks. Learn about the significance of return values to promises, how promises can be composed, and helper methods provided by popular promise libraries for that purpose. You will also see common promise anti-patterns and how bringing callback-oriented thinking to promises can cause you to miss out on opportunities to simplify your code.