Promises vs Async/Await
Promises provide the foundation for async operations. Async/await syntax offers cleaner, more readable code:
- Promises: .then() chaining (callback-based)
- Async/Await: synchronous-looking code
- Both handle asynchronous operations identically
- Async/await is syntactic sugar over promises
Async Functions
Async functions always return promises:
- async keyword marks function as asynchronous
- Can use await inside async functions only
- Implicitly return promise resolution
- Exception throws rejections
Error Handling
Use try-catch for error handling:
- Try block executes async code
- Catch block handles rejections
- Finally block runs regardless
- More readable than .catch() chains
Promise Chaining
Combine multiple async operations:
- Promise.all(): Wait for all promises
- Promise.race(): Complete at first promise
- Promise.allSettled(): All results regardless
- Promise.any(): First fulfilled promise
Common Patterns
- Fetch API: Browser HTTP requests
- setTimeout: Async delays
- Reading files: Async I/O operations
- Database queries: Async data retrieval
Conclusion
Async/await revolutionized asynchronous JavaScript programming, enabling developers to write clean, maintainable code that handles complex asynchronous operations elegantly.