The document discusses the challenges of asynchronous programming in JavaScript, particularly the issues with callbacks leading to callback hell. It introduces promises as a more manageable solution for handling asynchronous operations, emphasizing the ability to chain promises and collect results. The conclusion encourages further exploration of the topic through additional resources and demonstrations.

1. Promises and chaining
Into callback hell … back again

2. About Hans
@otype
hans@otype.de

4. Intro:
sync, async, callbacks

5. Humans are multi-threaded!

6. Javascript is single-threaded &
synchronous.
Browsers provide asynchrony*.

7. finish
start
a()
b()
c()
a()
b()
c()

8. finish
start
a()
b()
c()
a()
b()
c()
b()
a()
c()
c()
b()
a()
c(),a()
b()…

9. sync async

10. Why async?

11. Synchronous flow, here? Bad idea!

12. “Callbacks to the rescue!”

13. “Call me back!”

14. Use a callback! Way better!

15. Got it!

16. a() b() c() d() e() f()
Callbacks in order?

18. “Pyramid of doom!”

20. “I am NOT going to debug that!”

21. “Free ticket into callback hell!”

23. Core:
Promises to the rescue

24. “I hereby give you a promise that I
will answer your question some time
in the future … but not right now!”
My definition of a promise

25. Promise
fulfilled
rejected
pending
settled

26. Still experimental
kriskowal/q
cujojs/when
tildeio/rsvp.js
WinJS.Promise

27. $q.defer()

28. .then()

29. .resolve()
.reject()

30. .then() in .then() in .then() …

31. “I’ve seen that *$#%$* before …”

32. Chaining

33. “Wicked, Hans!”

34. “And what about collecting
results from multiple promises?”

35. Combined
results
$q.all()

37. “OK! Enough theory!”

38. Get fancy:
Demo Time!

39. Outro:
Questions?

40. http://ejohn.org/blog/how-javascript-timers-work/
http://www.html5rocks.com/en/tutorials/async/deferred/
https://docs.angularjs.org/api/ng/service/$q
https://github.com/kriskowal/q
https://developer.mozilla.org/en-US/docs/Web/JavaScript/
Reference/Global_Objects/Promise
https://www.promisejs.org/
https://github.com/promises-aplus/promises-spec

41. “Thank you! Over & out!”