What are the best practices for using promises in JavaScript?
Always handle errors, chain flatly (no nesting), always return from .then, use async/await for readability, use Promise.all for parallel operations, use Promise.allSettled for partial failure, do not wrap promises in new Promise, use .finally for cleanup, and parallelize independent operations.
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More FAQs in Promise Best Practices in JavaScript
Prefer async/await for readability. It makes async code look synchronous and uses try/catch for errors. Use .then chains when you need complex chaining or when async/await is not available.
Use .finally. It runs when the promise settles (fulfilled or rejected), regardless of outcome. Use it for hiding spinners, closing connections, resetting state. .finally does not receive the value or error.
When you want all results even if some promises reject. Promise.all rejects if any promise rejects (fast fail). Promise.allSettled waits for all and returns an array of { status, value/reason } objects, so you can handle partial failures.
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