Callbacks, promises, async, oh my! Asynchrony in JavaScript has come of age. We'll start with a quick history of the 3 techniques. Then dive in deep to async and await. How can you transition from callbacks to promises or promises to async? How can you use legacy code with await? How can your legacy code call your async functions? Whether you're using Babel or evergreen browsers, as Yoda would say, "async code write you can."