Come with me as I lead you from the pit of callback despair, up to the purgatorio of promises, and finishes in async heaven - using generators and yields to make async code look like sync code

1. From Callback Hell to Async
Heaven – Promises!
A Play in Three Acts:
Inferno, Purgatorio, and Paradiso

2. Act I: Inferno
THE ROAD TO HELL IS PAVED WITH
GOOD INTENTIONS

3. Our Journey Begins

4. Focusing on the Main Code

5. The Good and the Bad
Simple
Readable
Debuggable
Holds the Thread!
Not Async!

6. SO HOW DO WE RELEASE THE
THREAD?
Callbacks!

7. Good Intentions
CALLBACKS

8. Looks Good…

9. Doesn’t Look to Bad…

10. The Pyramid of Doom!

12. Our Code, In Hell

13. In Callback Hell, There are no Loops!

14. Act II: Purgatorio
BUT I PROMISE – IT GETS BETTER

15. Promises Instead of Callbacks

16. Chaining Promises

17. Easy Concurrency
ES6!

18. So How Do We Write promisedOpen?

19. Yes, But How do Promises Work?
• I don’t know
• And if I try to understand, my head hurts
• I just learn to accept it

20. Generalizing promisedOpen Across All
Node Functions
ES6!

21. So Where Does This Take Us?
Ugh…
Still no loop

22. Act III: Paradiso
PROMISES MUST BE KEPT –
ONWARD TO ASYNC HEAVEN!

23. BUT LET’S YIELD TO A LITTLE
DETOUR

24. Generator Functions

25. Iterator Protocol

26. We could have done it like this…
ES6!

27. But the ES6 compiler does it like this…

28. Bi-Directional Protocol

29. THIS IS WHERE IT BECOMES
MIND-BOGGLING

30. Can We Fulfill The Promise?

31. Sure!

32. So What About This?

33. No Problem!

34. Let’s Generalize

35. And… Async Heaven!

36. Compare

37. The Future

38. Epilogue
SO…

39. From Callback Hell

40. To Async Heaven

41. Our Journey is Complete
Thank You
https://github.com/giltayar/callback-to-async-
presentation