The Async JS Saga
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The document discusses various asynchronous patterns in JavaScript including callbacks, promises, generators and iterators, async/await, web workers, and observables. It notes that JavaScript is single-threaded and non-blocking, requiring asynchronous patterns. Callbacks are described as difficult for humans to follow while promises and async/await provide a more readable alternative. Generators and iterators allow breaking the run-to-completion model. Web workers run JavaScript in background threads without blocking the UI. Observables are suited for event streams and avoid memory leaks when implemented through libraries like RxJS.
The Async JS Saga
- 1. The Async JS Saga Harshit Juneja @sayhitoharshit
- 2. Async Patterns ● Callbacks ● Promises ● Generators and Iterators ● Generators and Iterators + promises ● Async-await ● Web workers ● Observables
- 3. What’s JS ? ● Single Threaded ● Non Blocking ● Asynchronous ● Concurrent
- 4. Callbacks
- 5. Callbacks
- 6. Then I got to know about this!
- 7. Problems with Callbacks ● Difficult to understand and plan for our sequential brain ● Implicitly hands over control to another party ● Trust Issues ● Callback Hell
- 9. Misconception about Callback Hell!
- 10. Enter Promises
- 11. Just Socially Acceptable Callbacks
- 13. Enter Generators and Iterators ● Python inspired concept ● Breaks Run-to-completion ● Easy on human brain
- 17. You still have callbacks!
- 19. Async-Await (The best of both worlds)
- 20. Web workers ● Use the Web Workers API ● Run your JS in background threads ● Non blocking : without interfering with the UI ● Useful for any large computations. ● Can send messages to JS code by posting messages to an event handler
- 22. Observables ● Suited for event streams ● Avoids memory leaks ● Implemented through external libraries (RxJS being the most used) ● Still to make it to the spec
Editor's Notes
- #4: When you execute something synchronously, you wait for it to finish before moving on to another task. When you execute something asynchronously, you can move on to another task before it finishes.