Promise .then() vs async/await
Two ways to handle asynchronous operations in JavaScript. async/await is built on Promises but offers cleaner syntax for sequential async flows.
| Feature | .then() chains | async/await |
|---|---|---|
| Syntax | promise.then(fn).catch(fn) | const result = await promise |
| Best for | Simple chains, parallel operations | Sequential async flows, complex logic |
| Debugging | Stack traces can be confusing | Clear stack traces |
| Readability | Can get messy with nested chains | Reads like synchronous code |
| Error handling | .catch() at end of chain | try/catch blocks |
| Parallel execution | Natural with Promise.all() | Need explicit Promise.all() |
Verdict
Use async/await for most async code — it is more readable and easier to debug. Use .then() for simple one-off chains or when you need the composability of promise chains.
Code Example
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Related Glossary Terms
A function passed as an argument to another function, to be executed later. Callbacks are the foundation of asynchronous JavaScript and are used extensively in event handling and array methods.
PromiseAn object representing the eventual completion or failure of an asynchronous operation. A Promise is in one of three states: pending, fulfilled, or rejected. Promises can be chained with .then() and .catch().
Async/AwaitSyntactic sugar built on top of Promises that makes asynchronous code look and behave like synchronous code. async functions always return a Promise, and await pauses execution until a Promise resolves.
Try/CatchA statement for handling runtime errors gracefully. Code in the try block is executed, and if it throws an error, execution jumps to the catch block. The finally block runs regardless of success or failure.