why code in node.js often get rejected by soundcloud
DESCRIPTION
From: http://gotocon.com/aarhus-2013/presentation/Why%20code%20in%20Node.js%20often%20gets%20rejected%20by%20SoundCloud At SoundCloud we ask candidates to send us some code before inviting them in for interviews. Candidates can use whatever language they want, and over the past years we saw a massive rise on the number of submissions using server-side JavaScript. Unfortunately, too many submissions are asynchronous blobs of procedural code. JavaScript is a fairly functional language, and over the past decades Functional Programming developed interesting solutions for many of the problems we face when writing Node.js and regular JavaScript. Let's talk about how to leverage good old Functional Programming techniques to make code less coupled and more readable!TRANSCRIPT
Why code in Node.js often get rejected by
SoundCloud
Phil Calçado - SoundCloud@pcalcado
http://philcalcado.comTuesday, October 1, 13
2011: Phil zieht nach Berlin
Tuesday, October 1, 13
Tuesday, October 1, 13
~ 200 million users / month
> 11 hours of audio uploaded every minute
Tuesday, October 1, 13
Tuesday, October 1, 13
http://bit.ly/15DToNK
hiring @ SoundCloud
Tuesday, October 1, 13
Phone
Code Review
Interviews
Offer
Tuesday, October 1, 13
Phone
Code Review
Interviews
Offer
Tuesday, October 1, 13
challenge until late 2012
Tuesday, October 1, 13
you can choose any language.
0
10
20
30
40
Ruby Java JavaScript (Node.js) C Clojure Scala
% of submissions ~2011-2012
Tuesday, October 1, 13
you can choose any language.
0
10
20
30
40
Ruby Java JavaScript (Node.js) C Clojure Scala
rejected before interview invited for inverview
Tuesday, October 1, 13
new challenge
Tuesday, October 1, 13
you can choose any language.
0
7.5
15
22.5
30
Ruby Java JavaScript (Node.js) Go Clojure Scala
% of submissions on the past ~1 year
Tuesday, October 1, 13
you can choose any language.
0
7.5
15
22.5
30
Ruby Java JavaScript (Node.js) Go Clojure Scala
% of submissions on the past ~1 year
Tuesday, October 1, 13
you can choose any language.
0
7.5
15
22.5
30
Ruby Java JavaScript (Node.js) Go Clojure Scala
rejected before interview invited for inverview
Tuesday, October 1, 13
you can choose any language.
0
7.5
15
22.5
30
Ruby Java JavaScript (Node.js) Go Clojure Scala
rejected before interview invited for inverview
WTF?
Tuesday, October 1, 13
http://bit.ly/J1aLNn
don’t get me wrong
we are all hipsters
Tuesday, October 1, 13
Tuesday, October 1, 13
Not OO, not Functional...Just (bad) Procedural code.
Tuesday, October 1, 13
we don’t need this complicated stuff.this is not java, you know.
Tuesday, October 1, 13
http://bit.ly/JiFSnq
so how do we structure our app?
Tuesday, October 1, 13
what to use?
(decent)procedures?
Tuesday, October 1, 13
Tuesday, October 1, 13
Tuesday, October 1, 13
what to use?
objects?
Tuesday, October 1, 13
Tuesday, October 1, 13
what to use?
...functions?
Tuesday, October 1, 13
http://bit.ly/JFbZt8Tuesday, October 1, 13
http://bit.ly/JFbZt8
“SICP and some of the Sussman & Steele "Lambda the ..." papers made a big impression on me years before, although I did not understand their full meaning then.Remember, I was recruited to "do Scheme" [...] My interest in languages such as Self informed a subversive agenda [...]. Likewise with first-class functions, which were inspired by Scheme [...]”
Tuesday, October 1, 13
Tuesday, October 1, 13
Tuesday, October 1, 13
Tuesday, October 1, 13
Tuesday, October 1, 13
Tuesday, October 1, 13
http://bit.ly/JiF7ef
going old school
Tuesday, October 1, 13
e.g. passing functions around
Tuesday, October 1, 13
we see a lot of this
Tuesday, October 1, 13
1st, we extract what is common
Tuesday, October 1, 13
then we refactor our functions
Tuesday, October 1, 13
and we send them as arguments
Tuesday, October 1, 13
e.g. closures not only for objects
Tuesday, October 1, 13
we see a lot of this
Tuesday, October 1, 13
we can keep writeComment as it is
Tuesday, October 1, 13
and we add a function with two closures
Tuesday, October 1, 13
and we add a function with two closures
immutable
Tuesday, October 1, 13
and we add a function with two closures
immutablemutable
Tuesday, October 1, 13
now we don’t need to pass in the kitchen sink
Tuesday, October 1, 13
e.g. functions all the way down
Tuesday, October 1, 13
we see a lot of this
Tuesday, October 1, 13
first we extract common protocol
Tuesday, October 1, 13
then we clean up our functions
Tuesday, October 1, 13
then we use them.
Tuesday, October 1, 13
then we use them. redundant?
Tuesday, October 1, 13
our “framework”:1 - Extract protocol in
“combinators”2 - Keep mutable state in
closures
Tuesday, October 1, 13
no scary monads required
Tuesday, October 1, 13
there is plenty to learn fromTuesday, October 1, 13
in the javascript community tooTuesday, October 1, 13
phil calçado
http://philcalcado.com@pcalcado
www.soundcloud.com
Tuesday, October 1, 13
How to Design Programs - http://bit.ly/K0BfrLStructure and Interpretation of Computer
Programs - http://bit.ly/K0BjYm
The Art of the Metaobject Protocol http://amzn.to/K0BqU1
Purely Functional Data Structures http://amzn.to/JFn4KG
Let Over Lambda - http://amzn.to/IMMkNO
An Introduction to Lambda Calculi for Computer Scientists - http://amzn.to/IX8d1B
All drawings are available as t-shirts from the awesome Diesel Sweeties - http://dieselsweeties.com/
Tuesday, October 1, 13