Do You Need Promise Chaining With Async/Await?

Promise chaining is a pattern for composing async logic using promises. You can chain promises together by putting a function that returns a promise as the `onFulfilled()` parameter to the `then()` function.

Promise chains are great for sequential operations with minimal branching. But they get unwieldy as soon as you start needing multiple async operations within an `if` statement or any other sort of significant branching. That’s where async/await comes in.

Async/await’s killer feature is that you can build async logic using CS101 concepts: for loops, if statements, try/catch. There’s nothing you can do with async/await that you can’t do with a sufficiently convoluted promise chain, but async/await makes your code much more readable.

However, you can mix promise chaining with async/await to get some neat design patterns. For example, Axios requests return complex nested response objects. What if you just want to get the JSON response body? You can combine `await` with a minimal promise chain.

There are also things you can do that you shouldn’t. A surefire way to look like an amateur is to put an async function as an `onFulfilled()` callback to `.then()`:

When you mix async functions and promise chains, make sure you use promise chains within an async function underneath an `await`. Don’t use an async function as an `onFulfilled()` callback, or, worse yet, use an async function as a promise executor. Promise chains can provide some convenience within async functions, but there’s no sense in nesting async functions in promise chains.