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Interviewing for a JavaScript Job

163 points by wallflower 12y ago

mesozoic 12y ago
Perhaps not unreadable but definitely way overly complex. I'd be much more happy with the 2-4 line solution that is obvious and move on to another question or work on then optimizing that for performance time or memory size.
- inglor 12y ago
  The candidate did not "optimize it for performance time or memory size". I love how the candidate integrates a lot of ES6 features and even basic algorithms into this. I would kill for candidates like this when I interview. It doesn't only show that they keep updated in the field which is important on its own - it shows that they understand the fundamentals. When I'm interviewing I _am_ interested in seeing this in a candidate. At the end of the day the candidate _did_ solve the problem.
  - figseed 12y ago
    The candidate may have solved the problem, but failed the task. At the outset, the interviewer placed a premium on time which the candidate ignored. The candidate made assumptions that the question was contrived therefore the solution offered was simply a place to make speaking points as well as test the interviewer's code literacy and as a result, spent the entire interview rewriting the system rather than filling in the blanks and moving on as asked. Did the candidate prove adequate experience? Sure. But at the day of the day, I feel the interviewer made a very reasonable decision to dismiss the candidate based on the fact that the response ignored the implied time constraint for the sake of adding superfluous nonsense. If I ask someone to fix a simple bug in some of my code and come back to see the code completely rewritten, 3 times the length with prince of darkness and tortoise and hare stuff mixed in, that would likely be the last time I ask them to touch my code.
    - nine_k 12y ago
      I don't see any mention of time constraints, except for "to save time, we have written some boilerplate for you". I wish my prospective employer clearly communicated key constraints like this. If I were the candidate, though, I'd first explain the idea of the solution (takes half a minute), then discussed ways to implement it (a minute or two), then went with a particular solution (counter, bitmap, two chasing indices, etc). I'd keep feedback from interviewers constantly flowing.
      - madeofpalk 12y ago
        Well, it's an interview. As both an interviewer and interviewee, you should be respectful that time is finite.
    - zipfle 12y ago
      The opening of the piece pretty clearly implied that the candidate did not have trouble finding work. The candidate made a good-faith effort to solve the question given in the interview while also using it as a tool to discover if this was a place where he'd like to work. Interviewers use filters like this question to weed out employees they don't want. What's wrong with interviewees using filters like code style and problem-solving priorities to weed out employers that wouldn't be a good fit?
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bootload 12y ago
"Writes unreadable code." Code is meant to be executed first, read second. Programmer A's reply was a terse, when Programmer B commented on some piece of code they couldn't understand. 'I can't read it, what does this do?' Code and its readability wasn't the problem.
- deleted 12y ago
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- jack9 12y ago
  > Code is meant to be executed first, read second. Knuth would disagree, as would anyone who had to maintain code...ever. Nowhere in the convoluted answer, did the carpenter explain the conceptual strategy of the solution. At least, that would have gotten a discussion going by replacing ??? with a comment. Instead they just chose to pontificate random aspects they considered important on a path that only they knew, assuming their approach was optimal (which it is not). That's pretty useless at any company.
- recursive 12y ago
  I have a different, yet equally unsupported view. Code is meant to be read first, executed second.
- eCa 12y ago
  > Code is meant to be executed first, read second. "Always code as if the person who ends up maintaining your code is a violent psychopath who knows where you live." [1] [1] http://c2.com/cgi/wiki?CodeForTheMaintainer http://c2.com/cgi/wiki?CodeForTheMaintainer
- collyw 12y ago
  That's why everyone changes binary files directly when they alter their code?
scotty79 12y ago
And all of that because he didn't notice that requirement was finite space not constant space. If someone asks you to buid a shed and you build space station then put it on their backyard for them to keep tools in don't be suprised that the answer you'll get is "We're not gonna pay for that". Anyway nice short story. Pleasent read.
- inglor 12y ago
  The protagonist didn't build them a space station - they have effectively shown understanding of the problem by reducing it to the problem it really is (cycle detection) showing them he understood the idea and not just how to solve it while using modern tools and correct abstractions (sequences, really). It's especially "provoking" since the author mentioned it was a Python shop and Python is _full_ of these - a lot of lazy sequences and generators all around and a community that understands them well too.
  - scotty79 12y ago
    Except that it's not about cycles detection in a linked list. It's about thing as simple as 'if I am where I have aleady been then I'm screwed'. You just need to remember stuff and recall it as quickly as possible, so hashmap. It's finite because size of the board is finite. End of story. His solution is just worse. His solution is slower because he picked inadequate data structures and he used algorithm for finding cycles that's only interesting because it can operate in fixed space but it's use is totally stupid because he constructs the linked list himself and that takes in worst case amount of memory proportional to number of fields on the board. It's a task you can figure out just by thinking few minutes about the problem without any prior knowledge so a good test question for checking your ability to think. The only reason you might come up with the solution OP presented is if you were told to 'do it as if js was haskell or something'
    - picks_at_nits 12y ago
      Where does the solution given use On space?
voyou 12y ago
The code here repeatedly defines functions which return an object with only one property, with the name being Symbol.iterator and the value being a generator function. Is there a reason to do this, rather than just writing a generator function directly?
- inglor 12y ago
  Well, you can't iterate a generator without invoking it. If you returned a generator you can't `for(let x of myGeneratorFn)` because it's not an iterable - rather a generator is just sugar for a function that returns an iterable. You'd have to do `for(let x of myGeneratorFn())` although in this case I agree it's silly to return it like this.
  - scotty79 12y ago
    He couldn't return generator instance because he needs two instances of game running at the same time for the tortoise and hare algorithm to run in const memory. He would need to return at least generator function but that would force him to invoke it before iterating.
- deleted 12y ago
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  - inglor 12y ago
    No you don't, you can Do `Array.from(myGeneratorFn())` or `[...myGeneratorFn()]` just fine - the difference is that you have to invoke it - you certainly _don't_ have to call .next to extract elements all the time manually.
    - picks_at_nits 12y ago
      Very true, You have to decide at some point whether you’re going to have everything be callable, or everything be an object, and thereafter be consistent. The functions `takeIterable` and `statefulMapIterableWith` are both written to take and return iterables, but you could write parallel versions operating directly on callables. You probably want them to return the same thing they consume. A more full-featured utility might pattern match on what it is given and return the same form.
scotty79 12y ago
Is there a point there to returning object with generator in the [Symbol.iterator] property instead of just the generator itself?
- inglor 12y ago
  Generally? Yes, for example for an array like data structure it would make sense to have methods on the data structure and make it iterable by providing a `Symbol.iterator` - in this case it can be avoided a generator is just a function that returns an iterable sequence (i.e. a sequence using the new ES iteration protocol) so usage would be different - you'd invoke it in a for...of instead of just iterating it.
  - scotty79 12y ago
    General usage I get. I just don't see the point of using it in this example. Everything else can be explained by 'I wan't my data structures to be immutable and lazy'. Symbol.iterator just seems like purposeless showing off. As for your last point, you wouldn't have to invoke in for...of if you returned generator instance, not generator function from your code.
    - madeofpalk 12y ago
      > Symbol.iterator just seems like purposeless showing off. That's the point.
ctaylor001 12y ago
I feel like this is a roman à clef and I'm missing the clef. What's the story with the repeated John Carpenter references?
- inglor 12y ago
  I think that this is the correct reference http://ntraft.com/the-carpenter-and-the-engineer/ http://ntraft.com/the-carpenter-and-the-engineer/
  - harlanlewis 12y ago
    > Some time later, The Carpenter ran into Bob Plissken at a local technology meet-up. “John! What happened at Thing?” Bob wanted to know, “I asked them what they thought of you, and all they would say was, Writes unreadable code. I thought it was a lock! I thought you’d finally make your escape from New York.” > The Carpenter smiled. “I forgot about them, it’s been a while. So, do They Live?”" The character's name is "John, The Carpenter". bob plissken - http://en.wikipedia.org/wiki/Snake_Plissken http://en.wikipedia.org/wiki/Snake_Plissken the thing - http://www.imdb.com/title/tt0084787/ http://www.imdb.com/title/tt0084787/ escape from new york - http://www.imdb.com/title/tt0082340/ http://www.imdb.com/title/tt0082340/ they live - http://www.imdb.com/title/tt0096256/ http://www.imdb.com/title/tt0096256/ FWIW, I don't get the connection to javascript interviews either.
    - tvmalsv 12y ago
      Let's not forget Assault on Precinct 13 (www.imdb.com/title/tt0074156/) and Christine (www.imdb.com/title/tt0085333/) :)
      - TheOtherHobbes 12y ago
        They Live is a Carpenter movie in which aliens in invisible pizza masks - you can see them if you have special magic shades - live among us and control us. https://www.youtube.com/watch?v=Wp_K8prLfso https://www.youtube.com/watch?v=Wp_K8prLfso And of course there's The Thing, which does an excellent job of explaining why you should you never allow important data to be mutable.
patmcguire 12y ago
I felt dumb not recognizing const, let, or the fat arrow as javascript constructs... Are they Firefox only? Or is Firefox the only one shipping the new standard? All my Googling only gives me Mozilla results; I do JS full time and haven't heard of these.
- __derek__ 12y ago
  Those are new in ECMAScript 2015 (f.k.a. ES6). Check out Kangax's compat table[1] for support. [1] http://kangax.github.io/compat-table/es6/ http://kangax.github.io/compat-table/es6/
- inglor 12y ago
  As the link in the article states you can use all of these with https://github.com/babel/babel https://github.com/babel/babel today, here is a quick and recent overview of new features http://www.2ality.com/2015/02/using-es6-today-minsk.html http://www.2ality.com/2015/02/using-es6-today-minsk.html
- jekrb 12y ago
  A nice set of slides explaining es6 syntax. https://speakerdeck.com/rauschma/using-ecmascript-6-today https://speakerdeck.com/rauschma/using-ecmascript-6-today
_RPM 12y ago
Hey I think this should be called "Interviewing for a JavaScript game developer job". Asking people to implement a game as a test to see if they know JavaScript is in my honest opinion not the best way to probe a person.
- myhf 12y ago
  They didn't ask him to implement a game. The game board was a metaphor for an arbitrary network of states.
  - wavefunction 12y ago
    If you're trying to solve this problem in JavaScript and it's not a game then I think you're doing something wrong(ly).
supercoder 12y ago
I would just leave if this actually came up in a real interview.
- deleted 12y ago
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- geebee 12y ago
  This sort of thing deters me from interviewing in the first place.
zaroth 12y ago
I'm obviously way behind the times here, but... what the heck have they done to Javascript?! Anyway... the worst case run-time of any algorithm I think is size-squared -- you have to look at every square. If you ever touch the same square twice, since the state of each square is constant, you have a loop. Therefore, either you use a bitmap to see if you've been there before, or just check if a move counter is greater than size-squared. If someone spent an hour discussing this problem in an interview, even if it seemed intelligible, honestly I doubt I would want to pursue it further.
- alisey 12y ago
  The question starts with: "Consider a finite checkerboard of unknown size", which means you don't know the value of size-squared. Bitmap requires O(n) space, while the Carpenter's solution requires only O(1) space. And both require O(n) time. If an interviewee failed to see the difference, honestly I doubt I would want to pursue it further.
  - Jare 12y ago
    "size" is perfectly known in the code. Before shooting off into functional rearchitecture land, a simple common sense question like "by unknown you mean arbitrary, right?" would have been more sensible. In addition, the candidate thinks "being asked to whiteboard code was an excuse to have a technical conversation with a future colleague" but spends the entire time having a monologue rather than a conversation, and seems pleased about it.
    - deleted 12y ago
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  - zaroth 12y ago
    Time and space complexity is obvious, and I agree I would want the interviewee to understand that. Like I said, the worst case is always the number of squares (just imagine the path of arrows walks through the entire board) so you can achieve O(1) space, O(n) time with just a move counter. What I missed is the requirement that you ignore the known upper bound, even though it's right there in the code, and so you can't use the move counter technique to achieve O(1)/O(n), you have to use the cycle-finding algorithm, which is slower but at least still not quadratic. "Your code should not presume anything about the gameboard’s size or contents, only that it is given an arrow every time though the while loop." It's not a bad question, but I think starting it off by asking them to write code inside the game function is a red herring. The function should be boxed off to return the sequence of arrows to start with, and then let the game begin. That way the requirements are clearly defined up-front. However, in my experience 0% of interviewees I've ever sat with, given such a function, ES6Fiddle and nothing else, would actually be able to implement Floyd's cycle finding from memory. Unless of course the recruiter prompted them to study it the night before. If you're adverse to providing full internet access during interviews (which I always do) then at least you would have to provide an excerpt from a relevant textbook or Wikipedia to set them on the right path.
joncalhoun 12y ago
This boiler plate code seems pretty bad to me. It is almost as if it was designed to trick candidates by giving them access to data they aren't supposed to use. The problem clearly states "The game board is hidden from us" yet the boiler plate code gives a developer access to the size of the board as well as the current position. It is as if the interviewer asked carpenter to solve problem A then gave him boiler plate code for problem B.
sirgawain33 12y ago
Unless I'm being thick, I think the point of this parable is to question the developer, not the interviewer. Despite using a bunch of fancy new language feature, name-dropping Knuth, and describing the solution for an hour, the result is code with no additional benefit and significantly worse maintainability. Sometimes being smart doesn't have to look so smart.
- supercoder 12y ago
  Looking at the previous posts by this author it looks as though he's got a very specific interest in playing with JavaScript language features. So I'm guessing this wasn't ever a real situation, just a fantasy story about how he'd love for an interview to play out.
  - picks_at_nits 12y ago
    And yet... At the end of the story, all three participants (recruiter, company, and candidate) have failed to get what they want. Somehow, this does not come across as a fantasy being played out, more of a cautionary tale.
    - supercoder 12y ago
      I dunno, the interviewer provides the template code as ECMAScript 2015 ? Seems incredibly bleeding edge for an interview question. And then the start of his reply is 'Using babeljs.io, I’ll write this in ECMASCript 2015 notation.', which is weird given the example code was already implied to be in this.
    - nostrademons 12y ago
      In the story, the very next day The Carpenter got a generous contract from FOG, a stealth startup doing very interesting work, and promptly forgot all about Thing. It sounds like he got exactly what he wanted.
      - picks_at_nits 12y ago
rayiner 12y ago
I personally think the answer here is fantastic. It shows several important things: the candidate keeps up to date with the tools, he thinks about problems formally and systematically, and has a solid grasp of theory. Not only did he decompose the original template into one that leverages existing utility functions, but written the solution in a mostly functional way where mutable state is localized in specific functions. You can easily extend his solution with more analyses. The interviewer asked a simple question designed to screen the clinically incompetent, and this guy used it as an opportunity to show the extent of his skills and knowledge, which is the whole point of an interview.
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- badc0de 12y ago
  I hope I never get to work with someone like the carpenter.
  - morenoh149 12y ago
    you're missing out. I hope to be the carpenter's apprentice!
  - codygman 12y ago
    Can you give some reasons why? Perhaps even show how you would have solved the problem?
- angersock 12y ago
  I'm not sure about you, but it took me until halfway into the reading to figure out that the interview was actually being honest. It may be just bad comprehension on my part, but the phrasing of the circumstances of the interview, as well as the way the interviewer spoke ("ECMAScript 2015"?), made me assume it was going to be some sort of satirical article. That, as well as the ball of code that was the boilerplate, made me assume that this was some kind of parody of actual interviews. It wasn't until I was reading through the tortoise-and-hare bit that I realized the author was actually being serious. Honestly, I'm kind of surprised that that kind of question even comes up in interviews--I think like easily 99% of a startup's tech problems are probably better reflected by "How do we handle rounded corners in legacy browsers" or "How do you provision a server because we can't afford AWS" or "What would you consider three essential libraries for Javascript on the backend, and why?". These CS questions just seem like underhanded trivia, especially when you dress up straightforward problem with a bunch of extra noise. They'd be fun to work through with an interviewee, as a way of seeing how they think about a problem, but just dropping it on them as sink-or-swim in a hostile environment doesn't seem very nice.
Falkon1313 12y ago
1) We will also need to hire a 'pretentious <-> English' translator just to communicate with this guy. He's probably also very opinionated and difficult to get along with. 2) His state-of-the-art code won't work on any of our deployed systems without lengthy and expensive upgrading or backporting. 3) We'll have to get all of our clients to upgrade their systems, or spend a ton of money and time adding compatibility layers. 4) None of our other developers will be able to maintain his code, and hiring someone to replace him would not be easy or cheap. 5) If we need to hire a 3rd-party agency for something, they wouldn't be able to work with him or his code either. It could cost us a fortune. He may be brilliant, but basically, we'll have to treat everything that he does as disposable, just as we would with a clueless newb who knows nothing about programming. And we can't entrust him with anything important.
- picks_at_nits 12y ago
  The story is really about what’s wrong with this process. You say the candidate should have written production code. And yet, this isn’t a production problem, it’s a made-up CS101 problem. How does it make sense to ask a CS101 question, but not accept a CS101 answer? Likewise, how does it make sense to give a CS101 answer without knowing what the interviewer is looking for in an answer? How do we know this is the code this person would write in production if we don’t give him a real-world problem to solve and ask him to solve it in a real-world way? If it’s legit to assume that this person only knows how to write theoretical code from one answer, it’s also legit to assume that the company only has theoretical problems to solve from one question. In reality, it’s insane to presume anything from one answer. If you want to know what this person writes in production, you ask about that. This is an experienced programmer being interviewed, how does it make sense to terminate the interview after asking one poorly-given question? Really, this is about a failure to communicate on both sides. For questions like this, if you don’t make it clear what you are looking for, you aren’t really testing their technical competence, you’re testing their ability to guess the answer you’re looking for. Likewise, if you aren’t given clear guidance about what kind of answer the interviewer is seeking, your responsibility is to ask for guidance, not to rush off and give the answer you think suits your agenda for showing off or for sparking the conversation you want to have. Failing either or both parties actually talking to each other, this isn’t a technical question at all.
badc0de 12y ago
I'm surprised why no one has mentioned the fact that the recruiter hinted the candidate and that the candidate could've prepared that convoluted answer beforehand. I would've certainly not hired him. Also, it is stupid to measure if a candidate knows some graph algorithm that you learn in CS 101 or some new js features that no one in their sane mind would use in prod, you should probably be more worried about thought process, concepts of modularity, maintenability and experience.
- Ronsenshi 12y ago
  I've noticed that too, but I don't really know if that is a common practice. It made me wonder what this Carpenter would do if he was not aware of possible questions or he was given something he was not prepared for.
- monokrome 12y ago
  Third-party recruiters will often hint these types of things, because it gives the candidate a better chance of success. After you interview, they will ask what you talked about and what kinds of questions you were asked. This allows them to keep track of how the company is interviewing, and to give the next candidate more information about what to expect. This will mean that the recruiter doing so will have a potentially higher rate of success than a recruiter not doing so, since the candidate has this benefit. Honestly, it's a pretty good thing. It's just good recruiters exploiting bad interviewers. It's better to design your interview around each candidate instead of recycling the same comp-sci questions that you heard in college over and over again. Companies are really just testing how often people interview in most cases, but don't realize how bad the process is. They are using the same questions that every other company uses instead of creating their own, and it usually doesn't find good candidates as much as it finds people who memorize interview questions.
Kiro 12y ago
So how would the expected answer look like? 1. Create an array of visited squares 2. Return false if square has been visited before, add current square to visited 3. Return true Would this be correct?
- thewarrior 12y ago
  Sort of. Store the squares in a hash map with the value used to indicate whether you've already seen it.
millstone 12y ago
I loved this post and also the HN comments, which show a wide variety of interpretations. My interpretation is that the article satirizes modern JavaScript development and startup culture, both of which are heavy on sizzle but lean on steak. It skewers the interviewer, who "intones" a highly refined question that's totally disconnected from the actual content of the position. But it also skewers the candidate, who happily provides an elaborately over-engineered solution that shows off "modern" JS development practices. The candidate and interviewer learn nothing from each other, but we are left certain that, if hired, the candidate's chief legacy will be a GitHub repo of a JavaScript MVC templating micro-framework that leverages JQuery and Backbone and...
- thewarrior 12y ago
  What is over engineered about his design ? It's actually well designed.
  - Ronsenshi 12y ago
    It certainly is marvelously designed, not too amazing considering that Carpenter knew that it is one of the possible questions and he prepared his answer beforehand. Anyway, judging by the provided code, Carpenter should have done only basic alteration to the original code in the marked spots (// ???) which should have been enough for the interviewer, so that they might have moved on to the next question if there was one: > Christine looked at the solution on the board, frowned, and glanced at the clock on the wall. “Well, where has the time gone?”
    - thewarrior 12y ago
      If this happened in real life it would be frikkin awesome. The interviewer would be flabbergasted. There are a couple of other blog posts in this genre : http://blogs.msdn.com/b/ericlippert/archive/2011/02/14/what-would-feynman-do.aspx http://blogs.msdn.com/b/ericlippert/archive/2011/02/14/what-... http://vk.com/note736369_9773341 http://vk.com/note736369_9773341
      - 12y ago
madsravn 12y ago
This article is a little weird. First we have this guy, who despite his experience "makes" the mistake of saying he can show something on the whiteboard. Why is that a mistake? And then we have this guy Bob - he coaches people what kind of questions they are asked at a given interview. So he is letting people get jobs which they might not even be suited for. I hope it is satire, as mentioned somewhere else.
aristidb 12y ago
I read this as a parable about abstracting & decomposing problems, and how lazy evaluation makes it easier. Also, about how you can write Haskell in Javascript.
jdauriemma 12y ago
If you engineer a solution for a terrible game and no one actually plays the game, does a problem really exist?
GhotiFish 12y ago
You know what. Criticisms and thoughts of this article aside, I do love thinking about problems, and solving problems. I feel gratified to get the jump from looping -> halting problem, (though the author obviously telegraphed it), and though I found the implementation he provided to be a touch over engineered, I did enjoy walking through with him. I agree with the majority of HN, but to be candid, I think I would of enjoyed being in Christine spot.

163 points by wallflower 12y ago

Perhaps not unreadable but definitely way overly complex. I'd be much more happy with the 2-4 line solution that is obvious and move on to another question or work on then optimizing that for performance time or memory size.

inglor 12y ago
The candidate did not "optimize it for performance time or memory size". I love how the candidate integrates a lot of ES6 features and even basic algorithms into this. I would kill for candidates like this when I interview. It doesn't only show that they keep updated in the field which is important on its own - it shows that they understand the fundamentals. When I'm interviewing I _am_ interested in seeing this in a candidate. At the end of the day the candidate _did_ solve the problem.
- figseed 12y ago
  The candidate may have solved the problem, but failed the task. At the outset, the interviewer placed a premium on time which the candidate ignored. The candidate made assumptions that the question was contrived therefore the solution offered was simply a place to make speaking points as well as test the interviewer's code literacy and as a result, spent the entire interview rewriting the system rather than filling in the blanks and moving on as asked. Did the candidate prove adequate experience? Sure. But at the day of the day, I feel the interviewer made a very reasonable decision to dismiss the candidate based on the fact that the response ignored the implied time constraint for the sake of adding superfluous nonsense. If I ask someone to fix a simple bug in some of my code and come back to see the code completely rewritten, 3 times the length with prince of darkness and tortoise and hare stuff mixed in, that would likely be the last time I ask them to touch my code.
  - nine_k 12y ago
    I don't see any mention of time constraints, except for "to save time, we have written some boilerplate for you". I wish my prospective employer clearly communicated key constraints like this. If I were the candidate, though, I'd first explain the idea of the solution (takes half a minute), then discussed ways to implement it (a minute or two), then went with a particular solution (counter, bitmap, two chasing indices, etc). I'd keep feedback from interviewers constantly flowing.
    - madeofpalk 12y ago
      Well, it's an interview. As both an interviewer and interviewee, you should be respectful that time is finite.
  - zipfle 12y ago
    The opening of the piece pretty clearly implied that the candidate did not have trouble finding work. The candidate made a good-faith effort to solve the question given in the interview while also using it as a tool to discover if this was a place where he'd like to work. Interviewers use filters like this question to weed out employees they don't want. What's wrong with interviewees using filters like code style and problem-solving priorities to weed out employers that wouldn't be a good fit?
deleted 12y ago
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bootload 12y ago

"Writes unreadable code." Code is meant to be executed first, read second. Programmer A's reply was a terse, when Programmer B commented on some piece of code they couldn't understand. 'I can't read it, what does this do?' Code and its readability wasn't the problem.

deleted 12y ago
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jack9 12y ago
> Code is meant to be executed first, read second. Knuth would disagree, as would anyone who had to maintain code...ever. Nowhere in the convoluted answer, did the carpenter explain the conceptual strategy of the solution. At least, that would have gotten a discussion going by replacing ??? with a comment. Instead they just chose to pontificate random aspects they considered important on a path that only they knew, assuming their approach was optimal (which it is not). That's pretty useless at any company.
recursive 12y ago
I have a different, yet equally unsupported view. Code is meant to be read first, executed second.
eCa 12y ago
> Code is meant to be executed first, read second. "Always code as if the person who ends up maintaining your code is a violent psychopath who knows where you live." [1] [1] http://c2.com/cgi/wiki?CodeForTheMaintainer http://c2.com/cgi/wiki?CodeForTheMaintainer
collyw 12y ago
That's why everyone changes binary files directly when they alter their code?

scotty79 12y ago

And all of that because he didn't notice that requirement was finite space not constant space. If someone asks you to buid a shed and you build space station then put it on their backyard for them to keep tools in don't be suprised that the answer you'll get is "We're not gonna pay for that". Anyway nice short story. Pleasent read.

inglor 12y ago
The protagonist didn't build them a space station - they have effectively shown understanding of the problem by reducing it to the problem it really is (cycle detection) showing them he understood the idea and not just how to solve it while using modern tools and correct abstractions (sequences, really). It's especially "provoking" since the author mentioned it was a Python shop and Python is _full_ of these - a lot of lazy sequences and generators all around and a community that understands them well too.
- scotty79 12y ago
  Except that it's not about cycles detection in a linked list. It's about thing as simple as 'if I am where I have aleady been then I'm screwed'. You just need to remember stuff and recall it as quickly as possible, so hashmap. It's finite because size of the board is finite. End of story. His solution is just worse. His solution is slower because he picked inadequate data structures and he used algorithm for finding cycles that's only interesting because it can operate in fixed space but it's use is totally stupid because he constructs the linked list himself and that takes in worst case amount of memory proportional to number of fields on the board. It's a task you can figure out just by thinking few minutes about the problem without any prior knowledge so a good test question for checking your ability to think. The only reason you might come up with the solution OP presented is if you were told to 'do it as if js was haskell or something'
  - picks_at_nits 12y ago
    Where does the solution given use On space?

voyou 12y ago

The code here repeatedly defines functions which return an object with only one property, with the name being Symbol.iterator and the value being a generator function. Is there a reason to do this, rather than just writing a generator function directly?

inglor 12y ago
Well, you can't iterate a generator without invoking it. If you returned a generator you can't `for(let x of myGeneratorFn)` because it's not an iterable - rather a generator is just sugar for a function that returns an iterable. You'd have to do `for(let x of myGeneratorFn())` although in this case I agree it's silly to return it like this.
- scotty79 12y ago
  He couldn't return generator instance because he needs two instances of game running at the same time for the tortoise and hare algorithm to run in const memory. He would need to return at least generator function but that would force him to invoke it before iterating.
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- inglor 12y ago
  No you don't, you can Do `Array.from(myGeneratorFn())` or `[...myGeneratorFn()]` just fine - the difference is that you have to invoke it - you certainly _don't_ have to call .next to extract elements all the time manually.
  - picks_at_nits 12y ago
    Very true, You have to decide at some point whether you’re going to have everything be callable, or everything be an object, and thereafter be consistent. The functions `takeIterable` and `statefulMapIterableWith` are both written to take and return iterables, but you could write parallel versions operating directly on callables. You probably want them to return the same thing they consume. A more full-featured utility might pattern match on what it is given and return the same form.

scotty79 12y ago

Is there a point there to returning object with generator in the [Symbol.iterator] property instead of just the generator itself?

inglor 12y ago
Generally? Yes, for example for an array like data structure it would make sense to have methods on the data structure and make it iterable by providing a `Symbol.iterator` - in this case it can be avoided a generator is just a function that returns an iterable sequence (i.e. a sequence using the new ES iteration protocol) so usage would be different - you'd invoke it in a for...of instead of just iterating it.
- scotty79 12y ago
  General usage I get. I just don't see the point of using it in this example. Everything else can be explained by 'I wan't my data structures to be immutable and lazy'. Symbol.iterator just seems like purposeless showing off. As for your last point, you wouldn't have to invoke in for...of if you returned generator instance, not generator function from your code.
  - madeofpalk 12y ago
    > Symbol.iterator just seems like purposeless showing off. That's the point.

ctaylor001 12y ago

I feel like this is a roman à clef and I'm missing the clef. What's the story with the repeated John Carpenter references?

inglor 12y ago
I think that this is the correct reference http://ntraft.com/the-carpenter-and-the-engineer/ http://ntraft.com/the-carpenter-and-the-engineer/
- harlanlewis 12y ago
  > Some time later, The Carpenter ran into Bob Plissken at a local technology meet-up. “John! What happened at Thing?” Bob wanted to know, “I asked them what they thought of you, and all they would say was, Writes unreadable code. I thought it was a lock! I thought you’d finally make your escape from New York.” > The Carpenter smiled. “I forgot about them, it’s been a while. So, do They Live?”" The character's name is "John, The Carpenter". bob plissken - http://en.wikipedia.org/wiki/Snake_Plissken http://en.wikipedia.org/wiki/Snake_Plissken the thing - http://www.imdb.com/title/tt0084787/ http://www.imdb.com/title/tt0084787/ escape from new york - http://www.imdb.com/title/tt0082340/ http://www.imdb.com/title/tt0082340/ they live - http://www.imdb.com/title/tt0096256/ http://www.imdb.com/title/tt0096256/ FWIW, I don't get the connection to javascript interviews either.
  - tvmalsv 12y ago
    Let's not forget Assault on Precinct 13 (www.imdb.com/title/tt0074156/) and Christine (www.imdb.com/title/tt0085333/) :)
    - TheOtherHobbes 12y ago
      They Live is a Carpenter movie in which aliens in invisible pizza masks - you can see them if you have special magic shades - live among us and control us. https://www.youtube.com/watch?v=Wp_K8prLfso https://www.youtube.com/watch?v=Wp_K8prLfso And of course there's The Thing, which does an excellent job of explaining why you should you never allow important data to be mutable.

patmcguire 12y ago

I felt dumb not recognizing const, let, or the fat arrow as javascript constructs... Are they Firefox only? Or is Firefox the only one shipping the new standard? All my Googling only gives me Mozilla results; I do JS full time and haven't heard of these.

__derek__ 12y ago
Those are new in ECMAScript 2015 (f.k.a. ES6). Check out Kangax's compat table[1] for support. [1] http://kangax.github.io/compat-table/es6/ http://kangax.github.io/compat-table/es6/
inglor 12y ago
As the link in the article states you can use all of these with https://github.com/babel/babel https://github.com/babel/babel today, here is a quick and recent overview of new features http://www.2ality.com/2015/02/using-es6-today-minsk.html http://www.2ality.com/2015/02/using-es6-today-minsk.html
jekrb 12y ago
A nice set of slides explaining es6 syntax. https://speakerdeck.com/rauschma/using-ecmascript-6-today https://speakerdeck.com/rauschma/using-ecmascript-6-today

_RPM 12y ago

Hey I think this should be called "Interviewing for a JavaScript game developer job". Asking people to implement a game as a test to see if they know JavaScript is in my honest opinion not the best way to probe a person.

myhf 12y ago
They didn't ask him to implement a game. The game board was a metaphor for an arbitrary network of states.
- wavefunction 12y ago
  If you're trying to solve this problem in JavaScript and it's not a game then I think you're doing something wrong(ly).

supercoder 12y ago

I would just leave if this actually came up in a real interview.

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geebee 12y ago
This sort of thing deters me from interviewing in the first place.

zaroth 12y ago

I'm obviously way behind the times here, but... what the heck have they done to Javascript?! Anyway... the worst case run-time of any algorithm I think is size-squared -- you have to look at every square. If you ever touch the same square twice, since the state of each square is constant, you have a loop. Therefore, either you use a bitmap to see if you've been there before, or just check if a move counter is greater than size-squared. If someone spent an hour discussing this problem in an interview, even if it seemed intelligible, honestly I doubt I would want to pursue it further.

alisey 12y ago
The question starts with: "Consider a finite checkerboard of unknown size", which means you don't know the value of size-squared. Bitmap requires O(n) space, while the Carpenter's solution requires only O(1) space. And both require O(n) time. If an interviewee failed to see the difference, honestly I doubt I would want to pursue it further.
- Jare 12y ago
  "size" is perfectly known in the code. Before shooting off into functional rearchitecture land, a simple common sense question like "by unknown you mean arbitrary, right?" would have been more sensible. In addition, the candidate thinks "being asked to whiteboard code was an excuse to have a technical conversation with a future colleague" but spends the entire time having a monologue rather than a conversation, and seems pleased about it.
  - deleted 12y ago
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- zaroth 12y ago
  Time and space complexity is obvious, and I agree I would want the interviewee to understand that. Like I said, the worst case is always the number of squares (just imagine the path of arrows walks through the entire board) so you can achieve O(1) space, O(n) time with just a move counter. What I missed is the requirement that you ignore the known upper bound, even though it's right there in the code, and so you can't use the move counter technique to achieve O(1)/O(n), you have to use the cycle-finding algorithm, which is slower but at least still not quadratic. "Your code should not presume anything about the gameboard’s size or contents, only that it is given an arrow every time though the while loop." It's not a bad question, but I think starting it off by asking them to write code inside the game function is a red herring. The function should be boxed off to return the sequence of arrows to start with, and then let the game begin. That way the requirements are clearly defined up-front. However, in my experience 0% of interviewees I've ever sat with, given such a function, ES6Fiddle and nothing else, would actually be able to implement Floyd's cycle finding from memory. Unless of course the recruiter prompted them to study it the night before. If you're adverse to providing full internet access during interviews (which I always do) then at least you would have to provide an excerpt from a relevant textbook or Wikipedia to set them on the right path.

joncalhoun 12y ago

This boiler plate code seems pretty bad to me. It is almost as if it was designed to trick candidates by giving them access to data they aren't supposed to use. The problem clearly states "The game board is hidden from us" yet the boiler plate code gives a developer access to the size of the board as well as the current position. It is as if the interviewer asked carpenter to solve problem A then gave him boiler plate code for problem B.

sirgawain33 12y ago

Unless I'm being thick, I think the point of this parable is to question the developer, not the interviewer. Despite using a bunch of fancy new language feature, name-dropping Knuth, and describing the solution for an hour, the result is code with no additional benefit and significantly worse maintainability. Sometimes being smart doesn't have to look so smart.

supercoder 12y ago
Looking at the previous posts by this author it looks as though he's got a very specific interest in playing with JavaScript language features. So I'm guessing this wasn't ever a real situation, just a fantasy story about how he'd love for an interview to play out.
- picks_at_nits 12y ago
  And yet... At the end of the story, all three participants (recruiter, company, and candidate) have failed to get what they want. Somehow, this does not come across as a fantasy being played out, more of a cautionary tale.
  - supercoder 12y ago
    I dunno, the interviewer provides the template code as ECMAScript 2015 ? Seems incredibly bleeding edge for an interview question. And then the start of his reply is 'Using babeljs.io, I’ll write this in ECMASCript 2015 notation.', which is weird given the example code was already implied to be in this.
  - nostrademons 12y ago
    In the story, the very next day The Carpenter got a generous contract from FOG, a stealth startup doing very interesting work, and promptly forgot all about Thing. It sounds like he got exactly what he wanted.
    - picks_at_nits 12y ago

rayiner 12y ago

I personally think the answer here is fantastic. It shows several important things: the candidate keeps up to date with the tools, he thinks about problems formally and systematically, and has a solid grasp of theory. Not only did he decompose the original template into one that leverages existing utility functions, but written the solution in a mostly functional way where mutable state is localized in specific functions. You can easily extend his solution with more analyses. The interviewer asked a simple question designed to screen the clinically incompetent, and this guy used it as an opportunity to show the extent of his skills and knowledge, which is the whole point of an interview.

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badc0de 12y ago
I hope I never get to work with someone like the carpenter.
- morenoh149 12y ago
  you're missing out. I hope to be the carpenter's apprentice!
- codygman 12y ago
  Can you give some reasons why? Perhaps even show how you would have solved the problem?
angersock 12y ago
I'm not sure about you, but it took me until halfway into the reading to figure out that the interview was actually being honest. It may be just bad comprehension on my part, but the phrasing of the circumstances of the interview, as well as the way the interviewer spoke ("ECMAScript 2015"?), made me assume it was going to be some sort of satirical article. That, as well as the ball of code that was the boilerplate, made me assume that this was some kind of parody of actual interviews. It wasn't until I was reading through the tortoise-and-hare bit that I realized the author was actually being serious. Honestly, I'm kind of surprised that that kind of question even comes up in interviews--I think like easily 99% of a startup's tech problems are probably better reflected by "How do we handle rounded corners in legacy browsers" or "How do you provision a server because we can't afford AWS" or "What would you consider three essential libraries for Javascript on the backend, and why?". These CS questions just seem like underhanded trivia, especially when you dress up straightforward problem with a bunch of extra noise. They'd be fun to work through with an interviewee, as a way of seeing how they think about a problem, but just dropping it on them as sink-or-swim in a hostile environment doesn't seem very nice.

Falkon1313 12y ago

1) We will also need to hire a 'pretentious <-> English' translator just to communicate with this guy. He's probably also very opinionated and difficult to get along with. 2) His state-of-the-art code won't work on any of our deployed systems without lengthy and expensive upgrading or backporting. 3) We'll have to get all of our clients to upgrade their systems, or spend a ton of money and time adding compatibility layers. 4) None of our other developers will be able to maintain his code, and hiring someone to replace him would not be easy or cheap. 5) If we need to hire a 3rd-party agency for something, they wouldn't be able to work with him or his code either. It could cost us a fortune. He may be brilliant, but basically, we'll have to treat everything that he does as disposable, just as we would with a clueless newb who knows nothing about programming. And we can't entrust him with anything important.

picks_at_nits 12y ago
The story is really about what’s wrong with this process. You say the candidate should have written production code. And yet, this isn’t a production problem, it’s a made-up CS101 problem. How does it make sense to ask a CS101 question, but not accept a CS101 answer? Likewise, how does it make sense to give a CS101 answer without knowing what the interviewer is looking for in an answer? How do we know this is the code this person would write in production if we don’t give him a real-world problem to solve and ask him to solve it in a real-world way? If it’s legit to assume that this person only knows how to write theoretical code from one answer, it’s also legit to assume that the company only has theoretical problems to solve from one question. In reality, it’s insane to presume anything from one answer. If you want to know what this person writes in production, you ask about that. This is an experienced programmer being interviewed, how does it make sense to terminate the interview after asking one poorly-given question? Really, this is about a failure to communicate on both sides. For questions like this, if you don’t make it clear what you are looking for, you aren’t really testing their technical competence, you’re testing their ability to guess the answer you’re looking for. Likewise, if you aren’t given clear guidance about what kind of answer the interviewer is seeking, your responsibility is to ask for guidance, not to rush off and give the answer you think suits your agenda for showing off or for sparking the conversation you want to have. Failing either or both parties actually talking to each other, this isn’t a technical question at all.

badc0de 12y ago

I'm surprised why no one has mentioned the fact that the recruiter hinted the candidate and that the candidate could've prepared that convoluted answer beforehand. I would've certainly not hired him. Also, it is stupid to measure if a candidate knows some graph algorithm that you learn in CS 101 or some new js features that no one in their sane mind would use in prod, you should probably be more worried about thought process, concepts of modularity, maintenability and experience.

Ronsenshi 12y ago
I've noticed that too, but I don't really know if that is a common practice. It made me wonder what this Carpenter would do if he was not aware of possible questions or he was given something he was not prepared for.
monokrome 12y ago
Third-party recruiters will often hint these types of things, because it gives the candidate a better chance of success. After you interview, they will ask what you talked about and what kinds of questions you were asked. This allows them to keep track of how the company is interviewing, and to give the next candidate more information about what to expect. This will mean that the recruiter doing so will have a potentially higher rate of success than a recruiter not doing so, since the candidate has this benefit. Honestly, it's a pretty good thing. It's just good recruiters exploiting bad interviewers. It's better to design your interview around each candidate instead of recycling the same comp-sci questions that you heard in college over and over again. Companies are really just testing how often people interview in most cases, but don't realize how bad the process is. They are using the same questions that every other company uses instead of creating their own, and it usually doesn't find good candidates as much as it finds people who memorize interview questions.

Kiro 12y ago

So how would the expected answer look like? 1. Create an array of visited squares 2. Return false if square has been visited before, add current square to visited 3. Return true Would this be correct?

thewarrior 12y ago
Sort of. Store the squares in a hash map with the value used to indicate whether you've already seen it.

millstone 12y ago

I loved this post and also the HN comments, which show a wide variety of interpretations. My interpretation is that the article satirizes modern JavaScript development and startup culture, both of which are heavy on sizzle but lean on steak. It skewers the interviewer, who "intones" a highly refined question that's totally disconnected from the actual content of the position. But it also skewers the candidate, who happily provides an elaborately over-engineered solution that shows off "modern" JS development practices. The candidate and interviewer learn nothing from each other, but we are left certain that, if hired, the candidate's chief legacy will be a GitHub repo of a JavaScript MVC templating micro-framework that leverages JQuery and Backbone and...

thewarrior 12y ago
What is over engineered about his design ? It's actually well designed.
- Ronsenshi 12y ago
  It certainly is marvelously designed, not too amazing considering that Carpenter knew that it is one of the possible questions and he prepared his answer beforehand. Anyway, judging by the provided code, Carpenter should have done only basic alteration to the original code in the marked spots (// ???) which should have been enough for the interviewer, so that they might have moved on to the next question if there was one: > Christine looked at the solution on the board, frowned, and glanced at the clock on the wall. “Well, where has the time gone?”
  - thewarrior 12y ago
    If this happened in real life it would be frikkin awesome. The interviewer would be flabbergasted. There are a couple of other blog posts in this genre : http://blogs.msdn.com/b/ericlippert/archive/2011/02/14/what-would-feynman-do.aspx http://blogs.msdn.com/b/ericlippert/archive/2011/02/14/what-... http://vk.com/note736369_9773341 http://vk.com/note736369_9773341
    - 12y ago

madsravn 12y ago

This article is a little weird. First we have this guy, who despite his experience "makes" the mistake of saying he can show something on the whiteboard. Why is that a mistake? And then we have this guy Bob - he coaches people what kind of questions they are asked at a given interview. So he is letting people get jobs which they might not even be suited for. I hope it is satire, as mentioned somewhere else.

aristidb 12y ago

I read this as a parable about abstracting & decomposing problems, and how lazy evaluation makes it easier. Also, about how you can write Haskell in Javascript.

jdauriemma 12y ago

If you engineer a solution for a terrible game and no one actually plays the game, does a problem really exist?

GhotiFish 12y ago

You know what. Criticisms and thoughts of this article aside, I do love thinking about problems, and solving problems. I feel gratified to get the jump from looping -> halting problem, (though the author obviously telegraphed it), and though I found the implementation he provided to be a touch over engineered, I did enjoy walking through with him. I agree with the majority of HN, but to be candid, I think I would of enjoyed being in Christine spot.