Five good interview questions for a web developer

Recently, I began working for the happiest company on earth, Disney. It’s only been a few weeks but I can already see the sophistication in the coding and web-development standards on my team. Ours is a young team and we’re still growing. Part of my duties have included interviewing potential team members, so I have been thinking a lot about web development technologies, processes, and concepts myself.

I wanted to share a handful of the questions I’ve come up with to gauge a potential team member’s skill set. And yes, I am aware it is possible that a candidate might hear my name, Google me and find this site, and thus be better-prepared for an interview. I’m okay with that; researching on the web is how most web devs learn their skills—and that includes interviewing!

1. What industry blogs and resources do you follow to keep your skills up?

This opener is great because it’s a softball and sets the candidate at ease. Plus, it provides insight into how deep they are into the web-development culture. A great answer would include a list of two or three blogs that they can name. Many candidates answer “lots of blogs” or “I just search for concepts,” etc. (a lá Sarah Palin’s answer to Katie Couric’s “which newspapers or magazines do you read?” question). Sure, we all search around and hit lots of sites that don’t stick in our head once we’ve found the answer or clicked through to somewhere else. But knowing the names of at least a couple resources shows that the candidate has a habit of following them consistently, not just searching when they need to remember the syntax of some function.

Personally, I read A List A Part, Smashing Magazine, Nettuts, and 52 Weeks of UX consistently, and a myriad other sites linked to from their articles.

2. What tools do use to develop your sites in, and why?

Another open-ended, “no wrong answers”-style question to keep the candidate talking. (A good interview is more about getting a sense of the person than just a list of answers, I think.) Here I am trying to learn about their development style. If they discuss their favorite text editor in great detail, that’s fine—especially if they talk about code snippets and tag completion that help them code more efficiently.

But a great answer would be one that addresses the conceptualization of a project, not just its implementation. Do they start with notepads and sharpies or a whiteboard to sketch out concepts and dataflows? That’s a perfectly valid answer! A well-rounded web developer should see the whole picture of a site, even if they don’t have to (get to?) think about the bigger picture in the position for which they’re applying.

And if they say they use Photoshop to design the page and the export the slices, you can pretty much thank them for their time and wrap the interview up.

3. Explain the difference between the javascript operators =, ==, and ===

Ah, the first right-or-wrong-answer question. This is a great one because it should quickly show you who you’re dealing with. If the candidate doesn’t know that a single equals sign is the assignment operator, it’s time to pretend that you just remembered you left the gas on at home and wrap things up.

Of course, the majority of developers will know the assignment operator and the second in the list, the comparison operator. It is true if both operands are equal.

But what about ===? That’s a trickier one, and candidates who know what it does are a cut above the others. For the record, it is a strict comparison operator that takes into account the type of the operands, not just their value. In javascript, for example, the values “4″ (with quotes, as a string) and 4 (no quotes, as a number) are equivalent with the comparison operator (==) but not equal under the strict comparison operator (===) that also compares types. (Want more info? Mozilla has this page explaining javascript operators).

4. Tell me what this CSS selector does: img[src=^photos]

CSS questions on web developer interviews can take many forms. Some show a bit of styled HTML and ask for the CSS to generate it. That’s great, but it’s time-consuming. I like this approach because it shows a relatively complicated CSS selector with an arcane option. Knowing that it is an attribute selector (in this case, for img elements) is a passable answer in my book. Also knowing that it selects img elements whose src attribute starts with the word “photos” earns bonus points. Writing a specific selector like this is somewhat rare, so not knowing that the caret (^) indicates “starts with” wouldn’t be a problem for me as long as they said something like “I’d have to look it up.”

5. Tell me some of the ways you can reduce the load time of a web application you’ve written?

This is another open-ended question that can allow the candidate to shine. I would look for any number of points to be touched on, including:

  • optimize images to be no greater than screen-resolution, and saved at a compression level that squeezes the file size as much as the visual integrity of the image will allow;
  • use CSS-based image sprites instead of multiple images to reduce HTTP requests;
  • eliminate images wherever possible and rely instead on robust CSS;
  • minimize all javascript files (using tools like jscompress.com or others) to reduce the amount of data transfered;
  • combine external javascript files to reduce HTTP requests;
  • watch the application load using a tool like YSlow or webkit’s resource inspector to identify any bottlenecks; and
  • analyze database queries and any javascript functions (especially any that iterate over the DOM) to see whether they could be optimized.

Obviously, there may be more answers to this question, but these are a good collection. I would also appreciate being surprised by a left-field answer I hadn’t considered.

That’s just the beginning

Five questions doesn’t an interview make, but these reveal a snapshot of a web developer’s skill and aptitude in a short interview. I estimate these questions would take about 20 to 30 minutes to answer, depending on the number of follow-up questions or how talkative the candidate is. But that’s not enough, so if you have some insightful web developer interview questions of your own, please share them in the comments!


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