If you have worked with Javascript before you might have been there already - callback hell! But there is an easy & elegant way out to get back control over your code - Promises and promise chaining! This talk will give an introduction to promises and chaining in AngularJS. This talk was held by Hans-Gunther Schmidt at the Berlin AngularJS Meetup on Oct. 8th 2014 (http://www.meetup.com/AngularJS-Meetup-Berlin/events/182646022/).

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!”