Frontend engineer Interview Questions


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Frontend Developer was asked...August 26, 2020

Easy quant and java questions

7 Answers

How long do they take to announce results of quiz round?

As soon as you submit the quiz u will get the mail... May be if you get shortlisted otherwise i don't know Less

Ty for your response. Do they confirm if I'm selected or not selected by mail?

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1. about 2. javascript typescript babel es5 es6 3. test driven development, unit-testing, continuous integration 4. react-redux, modern JS frameworks, JS closures 5. function sum(){/*add code here*/};console.log (sum(3)(5)(7)(3)()); // 18

4 Answers

function sum(x) { return function(y) { return function(z){ return function(w){ return function(){ return x + y + z + w; } } } } } Less

function mySum(val){ if(val === undefined) return val; return function(val2){ if(val2 === undefined) return val; return mySum(val + val2); } } Less

var sum = (n) => { let result = n; const fn = (n) => { if (n == null) { return result; } result += n; return fn; } return fn; } Less

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45 min Frontend question with HTML CSS and JavaScript. Have to make something.

3 Answers

Not going to give the question. Had to use mostly vanilla javascript including; setInterval, Math.floor, Array.slice, % operator and understand global vs function vs block scope. Bonus points for understanding request animation frame, this, and the event loop. If you get stuck explain to the engineer your solutions and why they dont work and ask for a hint. I had 2 hints and got the offer. The interviewer obviously knows the solution so dont try and outsmart them. Goodluck Less

Thanks for the information. This will definitely help one preparing for the interview :-) Less

Can you please provide more information on this ?


Round 1: Given a string and a style array render HTML pretty much like a rich text editor. For example: 'Hello, world', [[0, 2, 'i'], [4, 9, 'b'], [7, 10, 'u']] Output: '<i>Hel</i>l<b>o, w<u>orl</u></b><u>d</u> something like that.

3 Answers

I used a hash map and a stack to store the indices. I pushed the style into a stack and popped off when I hit the index. I had to write the output so I took care of not having invalid HTML having the <b> and <u> mixed up. This particular use case I had to take care. The interviewer gave me some hints around the hash map but I came up with the algorithm and implemented almost through the complete hour.</u></b> Less

You can answer it as an algorithm question. Or you can answer it like a true FEE by leveraging the platform. 1. Flatten the tags into a single array of open and close tag pairs. 2. Sort the flattened tags by injection index. 3. Insert tags in reverse order to preserve shifting index. 4. Join the string and pass it to innerHTML and let the browser handle the rest Less

Hey! I am trying to solve this problem. Can you give me some direction?


Design a modal from scratch using React

3 Answers

No DSA round for frontend

Can you please tell the CTC, It would be a great help.

Yes, please and your YOE


Experiences in angular and bootstrap

3 Answers


Only that's been asked ;) you even did not read the resume.

Thanks for highly interesting in my skills

Quovantis Technologies

Q What if I use var inside Contstructor function? function Person(firstName, lastName, age){this.firstName=firstName;this.lastName = lastName; var a = 5;}; What will console.log(a); print?

2 Answers

It will give compile time error, as you are using a variable outside of its scope. Less

I was not able to answer this


Find the length of longest contiguous sub-array where the sum of the elements in subarray is less than or equal to "k".

2 Answers

Didn't save my solutions, but it solved only 7 out of 10 of hackerrank's tests and for them, it wasn't enough. It had to do with time complexity/ Less

The key in these questions is to cover the fundamentals, and be ready for the back-and-forth with the interviewer. Might be worth doing a mock interview with one of the Canva or ex-Canva Frontend Engineer experts on Prepfully? They give real-world practice and guidance, which is pretty helpful. Less


Build a custom UI and debug.

2 Answers

There's quite an extended back and forth in actual interviews for questions like this, so nothing quite like real practice. The Prepfully Atlassian Frontend Software Engineer experts have actually worked in this role, so they're able to do an honest-to-God accurate mock, which really puts you through the paces. Less

Do projects with a framework for your choice. Understand how to use the debugger and browser tools. Less


The interview followed a standard format, where an input was given, and certain outputs expected. The inputs were presented in a file on the disk. As a javascript engineer, this was awkward, as javascript is rarely used to read/write directly to the hard drive. Due to NDA, I cannot disclose the specifics of the question itself.

2 Answers

I explained that although the challenge ideally required writing to/from disk for a "perfect solution", Javascript typically gets it's data input via HTTP, and displays its output via the browser, so that was how I would proceed with my solution. Less


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