Async Patterns in Node.js: Callbacks, Promises, Streams, and Events
Node.js has several async patterns beyond async/await. Here is what they are and when to use each.
Async Patterns in Node.js: Callbacks, Promises, Streams, and Events
Node.js has several async patterns beyond async/await. Here is what they are and when to use each.
async/await
For control flow in functions that need to wait for async operations. The default for most new code: clean, readable, easy to debug.
Promises
For parallel operations with Promise.all, error handling with .catch, and composing multiple async operations. The underlying mechanism beneath async/await.
Callbacks
For EventEmitter listeners, where you register a function that runs when an event fires. Also for older APIs. Not the default for new code, but still present in events.
Streams
For large data processing. Readable, writable, transform, and duplex streams process data in chunks instead of loading everything into memory. Used for files, HTTP, and large responses.
EventEmitter
For event-driven patterns. Emit custom events and listen for them. Many Node.js modules like streams and HTTP servers are built on EventEmitter.
When to Use Each
Use async/await for control flow. Use promises (Promise.all) for parallel operations. Use EventEmitter for event-driven patterns. Use streams for large data. Use callbacks for EventEmitter listeners and older APIs.
The Takeaway
Node.js async patterns: async/await for control flow, promises for parallel and composed operations, EventEmitter for event-driven patterns, streams for large data, and callbacks for events and older APIs. Each solves a different problem.
async/await for control flow, promises for parallel operations with Promise.all, callbacks for EventEmitter and older APIs, streams for large data processing, and EventEmitter for event-driven patterns. Each solves a different async problem.
For large data processing. Streams process data in chunks instead of loading everything into memory. Use them for large files, HTTP responses, and any data that should not be buffered entirely in memory.
For event-driven patterns, where you emit custom events and listen for them. Many Node.js modules like streams and HTTP servers are built on EventEmitter, so understanding it is key to using those modules.
A pattern for processing large data in chunks. Readable, writable, transform, and duplex streams process data as it flows through, instead of loading everything into memory at once. This keeps memory low for large inputs.
Use async/await for control flow. Use promises (Promise.all) for parallel operations. Use EventEmitter for event-driven patterns. Use streams for large data. Use callbacks for EventEmitter listeners and older APIs. Match the pattern to the problem.
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