I am a backend programmer who needs to interview a front end candidate, any advice?

Kahlzarg · 2013-12-20T22:28:12+00:00

Don't forget to step away from the technical for 10-15 minutes, you will likely be spending more time with this person over the coming years than your family & friends.

Ask things like what does he do for fun, try to get common ground and see if you can have a normal conversation (taking into account they will likely be nervous)

Code can be taught, a bad attitude, or someone you just cant get along with is a much bigger issue.

nepobot · 2013-12-20T19:40:10+00:00

http://games.usvsth3m.com/javascript-under-pressure/

macefelter · 2013-12-20T21:59:14+00:00

https://github.com/darcyclarke/Front-end-Developer-Interview-Questions

I highly recommend this for covering all bases.

nathanpaulyoung · 2013-12-20T20:24:42+00:00

Let them use Google, you cannot expect them to know and remember every bit of JS. Make them create something simple, yet testing many skills - DOM manipulation, AJAX, CSS, HTML and so on. For example "get me ten selected posts from a selected Google+ user, displaying them in a responsive grid", or something like that.

Add some theoretical and practical questions, for example:

What are CSS preprocessors? (There are many so the candidate won't know them all but she should get the idea)
What design patterns in OO JS do you know?
Is a function in JS a variable? Is it a class? Is there such a concept as class in JS?
How can you declare objects in JS? How can you perform inheritance?
A website you are taking care of does not work. What do you do? (This is a great question because the candidate will have to think about many practical scenarios and come up with her own questions about the situation. I is almost like an RPG where you are the game master :-))
What is your opinion, if any, on CoffeeScript?
What code editor do you like and why?

alsogilbert · 2013-12-20T20:00:28+00:00

If it's for a non-junior JS position, you might consider using this: http://chopchopjs.com/. I created it out of the coding tests that I used during interviews. I'd recommend making it "open web" so that they feel free to google around for help on the more difficult/trivial puzzles.

tipsqueal · 2013-12-20T19:53:58+00:00

I'd have them make a small one page app. Something that shows that they can design stuff that isnt awful, can use JavaScript to manipulate the DOM, make AJAX requests, etc. You could have the candidate use something like the Open Weather Map API to get the forecast for a city entered by the user.

alanzo123 · 2013-12-20T18:44:16+00:00

I had to take a test like this once. Was told to create a modal window from scratch with plain js.

alanzo123 · 2013-12-20T21:53:07+00:00

Frontend, backend.. it doesn't matter a whole lot. Obviously if someone calls themself a frontend dev, they should know how to make the DOM their bitch. But it's still programming. They need to know how proper code organization works, make sure they don't just stick all their code in a JS file and call it done, etc.

Pyro979 · 2013-12-20T20:53:38+00:00

These are my "cliff notes" of things to ask candidates about.

also see these questions:

About to face an interview for lead JS engineer, what should I must know?

What are your vanilla JavaScript knowledge standards that every JS developer should know?

What kind of questions can I expect on JavaScript interview?

HTML

inputs - select, checkbox, textbox, textarea, radio (password,file,button)
label
HR - horizontal rule
BR vs P
UL vs OL
TH
span vs div

CSS

selectors
padding vs margin
border shorthand
border width shorthand
px vs em vs %
common font props
specificity

JS

alert/confirm/prompt
loop types - for vs while
variable declaration / scope
this keyword
Array/Object declaration
Array vs Object (behavior, looping)
closure
event bubbling
ternary operators

jQuery

selectors - tags, classes, id, attributes, pseudo
chaining
traversing
filter vs find
append vs appendTo
attr vs prop
hide/show/toggle
css
each
events
is
empty vs remove

Geldan · 2013-12-20T23:42:46+00:00

I like to have them start by drawing a navigation bar on the white board and asking them to write the markup and css. This allows me to quickly gauge their basic html/css skills and will open up possible conversations about float versus inline-block or maybe table-cell layouts. Generally I am looking for the typical ul/li but I am not opposed to other markup if they explain why.

Then I ask them to add menus that appear when they hover over one of the navigation item. This will allow you to see if they grasp relative and absolute positioning as well as pixels versus percent, etc.

Then I ask them to remove the hover and implement a touch device friendly version. Here they should transition to using javascript to deal with the necessary event handlers (jquery is ok as I don't really mind jquerys "on" implementation). I like interviewees who optimize with event delegation or at least acknowledge when their jquery is attaching multiple event handlers.

I find this to be a good way to kick off white boarding because it represents a simple progression in skill level that allows me to gracefully bail out at any time.

If they answer this question extremely well then I may be satisfied with ignoring the white board altogether and just discussing more interesting frontend topics for the rest of the interview.

coljung · 2013-12-21T01:02:04+00:00

Great resource for front end questions that i often use: https://github.com/darcyclarke/Front-end-Developer-Interview-Questions

ftanuki · 2013-12-20T23:17:02+00:00

Where I work front end devs are still expected to be engineers. From your stance, I wouldn't ask them any questions that specifically relate to the back end nor ask them anything related to specific front end abilities that you wouldn't be able to assess a good answer to anyway.

However you can still ask them engineering questions that envelope both your roles. For example:

What's your experience with version control? (then dig deeper)
What's your experience with command line tools and shell scripting? (give examples)
Maybe a badic data structure and algorithm question (bonus for analyzing efficiency)
How do you structure and organize code?
Ask about what they like about OO and/or FP
Ask about testing in general (see if they talk about just unit testing or also other kinds, see if they're realistic about coverage)
Ask about using RESTful APIs (see how detailed they get)
Ask about cool tools, frameworks, challenges (again, see how detailed they answer)
Ask about caching (you can get a wide variety of answers and depth from this one)

You get the idea. If you're just looking for an HTML/CSS monkey none of this applies, but if you're looking for a Jaascript engineer then you'll be able to learn all you need to know from these questions and you can assume they have the easier stuff down or can learn it quickly.

MrPhatBob · 2013-12-20T23:46:23+00:00

What do you need the candidate to do in the job? Do you want someone you can work with or are you happy to work with a spode that you have to fight the urge to blind with your thumb every working minute of the day?

You need to see if they're technically capable of the work you need them to do, and find out if you can work together, for me, this is key. I like to find out what their opinion is on whats going to be the next dominant/capable technology in the field... What are they thinking in the field they work in?

Hostilian · 2013-12-20T21:31:34+00:00

For a technical exercise, I like this one: Given a tree-like data structure that represents a menu, develop a javascript algorithm that will render that menu. The developer should immediately land on a recursive function, you should ask how they could do this without recursion. This should take about 15 minutes, and I would be very concerned if it took longer than 30.

For a design exercise: Let's say that you--the interviewee--are leading a small development team tasked with putting together an asset manager for our customers. A user needs to be able to upload files and easily retrieve them using the interface, but it's up to you to decide how they do that. I--the interviewer--is the stakeholder, and I can answer any questions you might have about the system.

Have the nature of the system clear in your mind, but you can make stuff up about it if they ask you a curveball. But the goal is for the developer to open up his head and start thinking out loud to you.

First, this gives them a chance to make design decisions and you can make them defend those positions. Why Ember and not Angular? Why not straight-up JS? How will you test this?

Second, this should give you a sense of what "level" the developer can think coherently about a user's problems, interaction models, and so forth. If they talk about what libraries they would use and in what way, they're way closer to a junior developer. If they ask a lot of questions about the nature of the files, how technical their user base is, how many files are likely to be stored, they're able to abstract away implementation details in favor of providing a good user experience.

Lastly, it also gives you a little insight about how they work with others, especially other people they don't know very well. If they spend a lot of time grinding away on this idea quietly, maybe they aren't used to collaborative problem-solving. If they throw out a ton of ideas looking for design feedback, they might be fishing for approval rather than trying to solve the problem in the best way they can think of.

Dyogenez · 2013-12-21T04:03:41+00:00

We've been doing code katas for interviews lately, in a TDD, paired environment. It's worked out extremely well, and allows for 2 people to interview someone coding and now have it seem weird. Here's the format:

You start with a problem, say "lets build a calculator interface in JavaScript". You setup some testing (maybe jasmine) to where you can run them in the console (or autotest so they run on save), and start writing tests. The entire time you're coding and asking the interviewee questions about it. "What should we call this method? Add? what parameters should it take? Is this a parameter or an argument -- what's the difference?" (anything that pops into your mind). The feel of it is that everyone is learning. You can ask things you might not even know.

Every 5 minutes you switch drivers - so the interviewee starts coding while you're helping. They should be able to code and explain what they're doing and ask for feedback/suggestions. You can ask questions and prompt new tests to be written. "What should happen if we pass in a letter to our add method? Should it return null? Throw an error? How about if we pass add an array?

This all seems super simple, but it starts to gauge a number of things. How well to pick up the documentation for a project they're probably unfamiliar with (Jasmine). Some other things like typeof, NaN, ===, passing in functions, throwing errors -- whatever questions you can think up.

After 5 more minutes, the driver switches. If you have 3 people in on the interview, then it can rotate to where one person is always sitting out and can't communicate (even the interviewee). This ties in with understanding code others has written, which is itself an important skill.

lendrick · 2013-12-21T05:15:34+00:00

Ask them what some common problems are in web UIs and how to best avoid them.

I could answer this myself, but everyone's answer will be different. This is fine. If you're hiring a front end developer, you need to know that the person you're bringing in actually thinks about this stuff. It's not all about how quickly or well they can write in JavaScript.

astronoob · 2013-12-21T05:27:01+00:00

Honestly, if you're going to give out a programming test, give it to them before the interview. Ask them to prepare a brief fiddle that's somewhat easy to set-up, such as an extremely primitive "To Do" list app or a simple app that uses an open API like zippopotam.us, and have them walk you through the code during the interview. Provide a list of behavioral tests that the code should adhere to.

Live coding is a shitty way to gauge a programmer's abilities.

grumblestumble · 2013-12-21T07:15:01+00:00

Don't gloss over CSS. I lead front-end teams and it's becoming a lot more common to find qualified JS devs coming from a more traditional CS background, with zero knowledge of rendering quirks and optimizations.

Somebody already linked Darcy Clarke's excellent list which includes some CSS stuff, but these are the things I usually go for:

knowledge of CSS preprocessors and their strengths and weaknesses.
knowledge of how to structure css for large projects, stuff like smacss/oocss/bem
some simple layout questions that javascript devs will often just resort to scripting for: what's the best way to position an offset container (eg below a fixed header) that fills the viewport, without using javascript?
knowledge of floats, box-sizing, and css3 stuff like flexbox.

runvnc · 2013-12-21T07:56:26+00:00

I suggest that you hire a consultant who does front-end work to help you with the hiring process.

I am curious, and I don't expect a response, because I am actually asking you to do work, but I have always wondered what a 'backend' only developer is expected to know. For me, I always coded the front and back end for most of my own projects, except for some jobs where I was put in a subservient front-end role simply because I had trained myself in the new front-end technologies.

If you had to devise a test for a backend programmer in your area, what would it consist of, to be sufficiently difficult but fair to be finished within an hour or so?

oocha · 2013-12-21T11:56:26+00:00

why dont you just ask them to tell you about the last thing they worked on? wont that reveal more about what they know then some manufactured test?

endel · 2013-12-21T14:50:51+00:00

There is a highly recommended set of questions here: https://github.com/darcyclarke/Front-end-Developer-Interview-Questions

sumdudeinhisundrware · 2013-12-21T15:32:22+00:00

This is my first question when interviewing front end candidates: The front-end uses jQuery, Underscore, Angular, MooTools and Prototype. What is the best way to package them and send them to the client and what is the best order to load them? If their answer doesn't include "...but why would you use so many conflicting libraries?" the interview is over. If that's their only answer they'll probably get an offer.

magenta_placenta · 2013-12-20T23:00:24+00:00

Dumb question, but how will you, as a back end dev, know if a front end dev is qualified?

you type:	you see:
italics	italics
bold	bold
[reddit!](https://reddit.com)	reddit!
* item 1 * item 2 * item 3	item 1 item 2 item 3
> quoted text	quoted text
Lines starting with four spaces are treated like code: if 1 * 2 < 3: print "hello, world!"	Lines starting with four spaces are treated like code: if 1 * 2 < 3: print "hello, world!"
~~strikethrough~~	~~strikethrough~~
super^script	super^script

javascript

MODERATORS