Front End Developer Interview Questions

Front End Developer Interview Questions

Front end developers are responsible for the interaction between web pages and users by designing and creating webpages using HTML, CSS, and JavaScript. Knowledge and experience with these three programming languages and their supporting tools is a must for employers. During an interview, be prepared to answer technical questions and to talk about past web development experience.

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Bloomberg L.P.
Front End Web Developer was asked...February 23, 2010

What is a JavaScript callback function?

5 Answers

A callback function is a piece of JavaScript code that executes after the main function that the callback is attached to executes successfully. Less

udaykanth, I would say that a .forEach() would be the most common and most basic use of a callback function. I'm just writing this to help anyone that might have a hard time thinking up a quick example if the come across this question themselves. Example: var numArray = [ 1, 2, 3 ] ; numArray.forEach( function( i ) { console.log( arr[ i - 1 ] ) } ) ; // logs out // 1 // 2 // 3 Less

I don't think Bloomberg is a very good company. I am an excellent web developer and have gotten multiple offers from other companies with big names, but was rejected by Bloomberg. They are too demanding during the job interview and it becomes a game of how well you can interview as opposed to how talented an employee you are and how much you can contribute to the growth of the company. Less

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How to center a 200px x 200px div to the center of the screen?

2 Answers

Provide top and left 50% then off set the div with -100px margin top and left. A more scaleable solution would be to use transform: translate(-50%, -50%) to make it not matter what size the div is. Less

<div> <div> Inner </div> <div> .outer { width: 100vw; height: 100vh; position: relative; } .inner{ width: 200px; height: 200px; position: absolute; left: 0; right: 0; top: 0; bottom: 0; margin: auto; }</div></div> Less


As a designer, did I think I would get bored with coding and troubleshooting?

1 Answers

I let them know that while design is a creative field, I have always been interested in designing for the user, and coding is no different. Whether creating a design or writing code the interesting part to me was the end result for the user. Less


Say there was a function that took 1 second to execute and you needed to run this function 10 million times, how would you cut down on the execution time?

1 Answers

Build a system that would run the functions concurrently.

IXL Learning

Given a number n where n+1 and n-1 are prime, prove n is divisible by 6

1 Answers

n+1 is prime, n+2 is prime... all prime numbers are odd, so n must be even (i.e., divisible by 2) in any set of 3 numbers (consider 1,2,3 or 4,5,6 or 20,21,22) at least one number is divisible by 3. since n+1 and n+2 can't be divisible by anything, n must be divisible by 3. therefore n is div by 6 Less


If we wanted to implement a method of tracking every click that the user made on the site, how would we want to do this?

1 Answers

Place a JavaScript event listener for all clicks at the document level. Perform actions based on the details of the click. This problem had multiple branches and sub-questions, but the gist is that you would want to capture the events as they bubbled back up to the document level. There are other acceptable answers to this question. Less


What is== and === operator?

1 Answers

== returns a Boolean true if both the operands are equal. === this is the strict equal operator and only returns a Boolean true if both the operands are equal and of the same type. Less


What are your greatest technical strengths?

8 Answers


Social media experience

I am technically sound in using R script for R programming language, base SAS, SAS analytics and Advanced SAS. Less

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// Given var endorsements = [ { skill: 'css', user: 'Bill' }, { skill: 'javascript', user: 'Chad' }, { skill: 'javascript', user: 'Bill' }, { skill: 'css', user: 'Sue' }, { skill: 'javascript', user: 'Sue' }, { skill: 'html', user: 'Sue' } ]; getSkills = (endorsements) => { // Result // [ // { skill: 'javascript', user: ['Chad', 'Bill', 'Sue'], count: 3 }, // { skill: 'css', user: ['Sue', 'Bill'], count: 2 }, // { skill: 'html', user: ['Sue'], count: 1 } // ]; } see this image:

7 Answers

let endorsements = [ { skill: 'css', user: 'Bill' }, { skill: 'javascript', user: 'Chad' }, { skill: 'javascript', user: 'Bill' }, { skill: 'css', user: 'Sue' }, { skill: 'javascript', user: 'Sue' }, { skill: 'html', user: 'Sue' }, ]; let x = endorsements.reduce((acc, { skill, user }) =&gt; { if (skill in acc) { acc[skill] = { user: [...acc[skill]['user'], user], count: acc[skill]['count'] + 1, skill: skill, }; } else { acc[skill] = { user: [user], count: 1, skill: skill, }; } return acc; }, {}); console.log(Object.values(x)); Less

I did in a different way let outPut = []; let skillMap = {}; for (let char of endorsements) { if (char['skill'] in skillMap) { skillMap[char['skill']] = [...skillMap[char['skill']], char['user']]; } else { skillMap[char['skill']] = [char['user']]; } } for (let key in skillMap) { let skillObj = {}; skillObj['skill'] = key; skillObj['user'] = skillMap[key]; skillObj['count'] = skillMap[key].length; outPut.push(skillObj); } return outPut.sort((a, b) =&gt; b.count - a.count); Less

getSkills = endorsements =&gt; { const skillMap = {}; // assumption - each object has all the properties, nothing is missing endorsements.forEach((item, index) =&gt; { const { skill, user } = item; if (!skillMap[skill]) { skillMap[skill] = {}; skillMap[skill]["user"] = []; // skillMap[skill]["user"].push(user); skillMap[skill]["count"] = 0; } skillMap[skill]["user"].push(user); skillMap[skill]["count"] += 1; // } }); return Object.keys(skillMap).map(key =&gt; [ { skill: key, ...skillMap[key] } ]); }; Less

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In your opinion, what is our company's single most important metric?

7 Answers

Reservations per day I guess

It's always revenue my man/woman

"It's always revenue my man/woman." I hope you understand how irrelevant you observation is in the context of this position. So no, it's not "always revenue." Less

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