Slides from my 2014 MounainWestJS talk "Add some Fun to Your Functional Programming With RXJS"

1. Add some FUN to your
Functional programming
with RXJS

2. Java…
Groovy…
and JavaScript
Senior UI Engineer at Netflix
We do a lot of RX stuff with…
About Me

3. bittersweetryan
About Me

4. Before We Begin

5. Before We Begin
Be KIND to those of us with OCD and…

6. Before We Begin
Change those Dropbox icons to B&W!

7. Functional Review!
(With an RX twist)

8. Functional Review
Map
Reduce
Filter
Zip

9. var searchResultsSets =
keyups.
map( function( key ){
return Observable.getJSON('/search?' +
input.value)
});
Functional Review
Map - Transforms data

10. var searchResultsSets = keyups.
filter( function ( key ){
return input.value.length > 1;
}).
map( function( key ){
return Observable.getJSON('/search?' +
input.value)
);
Functional Review
Filter - Narrows Collections

11. var html =
searchResultsSets.
reduce(function( prev,curr ) {
return prev + '<li>' + curr.name + '</li>';
},'' );
Functional Review
Reduce - Turns a collection into a single value

12. Functional Review
Zip - Combines two collections
var movies = [ 'Super Troopers', 'Pulp Fiction',
'Fargo' ] ;
var boxArts =[ '/cdn/23212/120x80',
'/cdn/73212/120x80','/cdn/99212/120x80' ] ;
!
var withArt = Observable.
zip(movies, boxarts, function(movie, boxart){
return {title : movie, boxart : boxart};
});
!
//[{title : 'Super Troo…', boxart : '/cdn…'},
// {title : 'Pulp Fict…', boxart : '/cdn…' },
// {title : 'Fargo', boxart : 'cdn…' } ]

13. Functional Review
Observable Data Streams Are Like Crazy Straws
keyPresses Observable
forEach
throttle
filter
map
distinctUntilChanged
reduce

14. Thinking Functionally!
!

15. Thinking Functionally
Replace loops with map, reduce, and filter.
searchResults = Observable.
getJSON(‘/people?’ + input.value);
!
searchResults.
forEach( function( reps ){
var names = [];
for( var i = 1; i < resp; i++ ){
var name = data[i].fName + ' ' +
data[i].lName;
names.push( name );
}
});

16. Thinking Functionally
Replace loops with map and reduce.
searchResults = Observable.
getJSON(‘/people?’ + input.value).
map( function( data ){
return data.fName + data.lName;
} );
!
searchResults.forEach( function( resp ){
//resp will now be the names array
})

17. Thinking Functionally
Replace if’s with filters.
var keyPresses = O.fromEvent( el, 'keyup' )
!
keyPresses.forEach( function( e ){
if( e.which === keys.enter ){ //=> no!
//do something
}
});

18. Thinking Functionally
Replace if’s with filters.
var enterPresses = O.fromEvent( el, 'keyup' )
.filter( function( e ){
return e.which && e.which === keys.enter;
});
!
enterPresses.forEach( function( e ){
//do something
});

19. Thinking Functionally
Don’t put too much in a single stream.
var submits = O.fromEvent(input,'keypresses').
throttle().
map( function( e ){
return e.which
} ).
filter( function( key ){
return key === keys.enter || keys.escape;
}).
map().
reduce().
...
Smaller streams are OK.

20. Thinking Functionally
var submits =
Observable.fromEvent(input,'keypresses').
throttle().
map( function( e ){
return e.which
} );
!
var enters = submits.filter( function( key ) ){
return e.which === keys.enter;
}
!
var escapes = submits.filter( function( key ) ){
Don’t put too much in a single stream.
Smaller streams are OK.

21. Flattening Patterns!
managing concurrency!

22. Observables = Events Over Time
Key presses over time…
.5s 1s 1.5s 2s 2.5s 3s
B R E A K IJ <- N G B A D

23. Observables = Events Over Time
1s 2s 3s 4s 5s 6s
BR
BRE
BREAK
BREAKJ
BREAKING
BREAKING BA
BREAKING BAD
Ajax requests over time…

24. The Three Musketeers
Goofy as merge
Donald as concat
Mickey as switchLatest
Starring

25. Flattening Patterns
merge - combines items in a collection as each item arrives
concat - combines collections in the order they arrived
switchLatest - switches to the latest collection that !
arrives

26. Merge
1s 2s
http://jsbin.com/wehusi/13/edit
data
data
data
data

27. Concat
1s 2s
http://jsbin.com/fejod/4/edit
!
!
data
data
data
data

28. SwitchLatest
!
1s 2s
data
data
data
data

29. Building Animated
AutoComplete!
Putting Everything Together

30. Animated Autocomplete
SearchBBrBreBreaBreak

31. Observables = Events Over Time
Simple Widget, High Complexity
• Respond to key presses
• Send off Ajax requests
• Animate out when search results become invalid
• Animate in when new search results come in
• Don’t show old results
• Make sure one animation is finished before starting
another

32. var keyups =
Observable.
fromEvent( searchInput, 'keypress');
Animated Autocomplete

33. var searchResultsSets =
keyups.
filter( function ( e ){
return input.value.length > 1;
}).
map( function( e ){
return Observable.
getJSON('/search?' + input.value);
}).
switchLatest();
Animated Autocomplete

34. var animateOuts =
keyups.
map(function( resultSet ){
return animateOut(resultsDiv);
});
!
var animateIns =
searchResultsSets.
map( function( resultSet ){
return Observable.
of(resultsSet).
concat(animateIn(resultsDiv));
});
Animated Autocomplete

35. var resultSets =
animateOuts.
merge(animateIns).
concatAll();
!
resultSets.
forEach( function( resultSet ){
if (resultSet.length === 0) {
$('.search-results').addClass('hidden');
}
else {
resultsDiv.innerHTML = toHTML(resultSet );
}
} );
Animated Autocomplete

36. var keyups =
Observable.
fromEvent( searchInput, ‘keypress');
!var searchResultsSets =
keyups.
filter( function ( e ){
return input.value.length > 1;
}).
map( function( e ){
return Observable.
getJSON('/search?' + input.value);
}).
switchLatest();
var animateOuts =
keyups.
map(function( resultSet ){
return animateOut(resultsDiv);
});
!var animateIns =
searchResultsSets.
map( function( resultSet ){
return Observable.
of(resultsSet).
concat(animateIn(resultsDiv));
});
!var resultSets =
animateOuts.
merge(animateIns).
concatAll();
!resultSets.
forEach( function( resultSet ){
if (resultSet.length === 0) {
$('.search-results').addClass('hidden');
}
else {
resultsDiv.innerHTML = toHTML(resultSet );
}
} );
Animated Autocomplete

37. Thank You.!
!
ranklam@netflix.com
@bittersweetryan!