Frontend Engineer Interview Guide

The initial phone interview with a hiring manager is typically the more straightforward stage in the hiring process. 

This is because hiring managers tend to follow a somewhat conventional format for these interviews. This predictability can work to your advantage because it allows you to prepare more effectively. You can often anticipate the type of questions they will ask, such as inquiries about your experience, your motivation for applying, and your understanding of the company and its culture.

Secondly, many of the questions in these phone interviews are behavioral. These questions aim to assess your soft skills, teamwork abilities, and how well you'd fit into the company culture. If you have a good grasp of the company's values, mission, and the specific role you're applying for, you can tailor your answers to align with their expectations.

Plus, when you get this initial call, remember that they're usually flexible with interview scheduling. So, if you need some time to prepare or adjust the date and time to your convenience, don't hesitate to communicate that.

The Technical Phone Interview for front-end developers typically consists of 1 to 3 phone/video technical interviews with your potential teammates. 

The focus of these interviews can differ significantly. Some companies place a strong emphasis on data structures and algorithms, while others concentrate solely on front-end technologies. It's a good idea to reach out to recruiters in advance to get a clear idea of what you'll be tested on. Frontend is incredibly broad, and it's therefore very important to make sure you're prepared for the right part of the ecosystem you'll be tested in.

The most common thing to be tested is your problem-solving skills. They'll often ask you to solve a coding problem using a shared document or a code editor. Sometimes, they might modify the problem statement to assess how you adapt to new conditions, so flexibility in your problem-solving approach is valuable. For instance, an interviewer might add a new constraint (eg. the browser you're optimizing for is Edge) or dimension (eg. this will be accessed concurrently by more than a 100 million users, how would you change your approach)

When it comes to the technical phone screen, make sure you choose a programming language you're comfortable with, preferably Python, Java, or C++ since these are commonly accepted Object-Oriented Programming languages. 

In addition to coding problems, you might also face a few theoretical questions related to front-end development.

In some cases, companies may request you to complete a coding assignment—for which you'll be given a couple of days. Since the interviewers have ample time to review your code, it's crucial to write clean and well-tested code. Additionally, investing in good UI/UX design for your solution can make a positive impression. 6 quick tips to ensuring you approach this the right way:

1. Prioritize functionality by implementing core features before focusing on aesthetics or optimizations. What's most important is that your assignment solves the problem being asked of you.
2. Write clean, well-commented code to ensure it's easily understood and maintainable for reviewers. Adding a readme is a simple touch but which reviewers really appreciate.
3. Test across multiple browsers and devices. Make sure your work is mobile responsive.
4. Use version control with meaningful commit messages to track progress and changes effectively.
5. Implement modular and reusable components to demonstrate good architecture practices.
6. Review the assignment's requirements and guidelines thoroughly before starting to ensure all deliverables are met. You can always ask for clarifications if you really need, it's better to ask rather than to assume.

One general piece of advice: attempting to cheat or take shortcuts during this stage is a bad idea. It's better to do your best and demonstrate your genuine skills, as dishonesty will simply lead to embarrassing situations during an onsite interview. It's pretty easy for experienced interviewers to make out when your code's just been copied or "GPT-generated".

The on-site interview for front-end developers is the ultimate test of your technical skills and overall fit for the company. You can also prepare by reviewing the Uber Front-End Engineer and Doordash Engineering Manager Interview Guide guides. It typically consists of three major rounds:

1. The Coding Round: This round is about assessing your technical prowess. You can expect to solve one or two problems related to algorithms and core data structures. Questions might revolve around arrays, strings, trees, graphs, or dynamic programming. Remember, the key is not just finding the solution but also being able to explain your thought process and approach clearly.
   
2. The Frontend Design/Architecture Round: This round is quite different from your typical coding interview. It's a 45-minute session where you won't be writing any code. Instead, you'll be tackling a broad design problem using a whiteboard for some visual aid. The focus here is not on coding skills but on your ability to solve complex engineering design problems. It's not your usual System Design interview; think of it more like "Frontend System Design." They want to see if you can architect solutions for higher-level problems that involve connecting various frontend concepts. For instance, they might give you a scenario where you have to come up with a solid architecture for a web app. The catch? It should be able to handle a ton of data efficiently while keeping the user experience smooth. You'll need to show that you understand stuff like browsers, the DOM, performance, API design, and so on.
   
3. The Behavioral Round: The behavioral round focuses on your attitude and how well you fit within the company culture. You'll be asked questions about workplace situations and your past experiences. Expect inquiries about challenging projects you've worked on, conflicts with colleagues or managers, how you maintain work-life balance, and so on.
   
   When you are preparing for a Frontend Engineer Interview - we’d recommend keeping these things in mind:

• Dive into the company's culture, values, and goals. Align them with your career aspirations to showcase genuine interest.
• Bring up alternative solutions, delving into their major tradeoffs. Demonstrate your ability to make informed decisions balancing various considerations.
• If you've mainly worked with UI libraries, take time to explore raw DOM APIs. For those relying on utility libraries like Lodash, try implementing some methods from scratch. Test solutions with large inputs, considering memory consumption and edge cases.
• Brush up on data structures (lists, arrays, hash tables, etc.) and algorithms. Be ready to discuss Big O complexity, sorting, searching, traversals (BFS, DFS), recursion, and iterative approaches.
• Ensure a strong grasp of JavaScript fundamentals – variables, functions, objects, arrays, asynchronous control flow, and closures.
• Organize your thoughts using the SOAR method (Situation, Objective, Action, Result). It helps present a well-thought-out and chronological narrative during interviews.

Interview Questions

• What is your current favorite mobile app, and why?
• What is a CSS grid system?
• How do you handle situations where too much is put on your plate?
• What is a pseudo-class?
• How do you approach disagreements with your manager?
• What is a CSS reset?
• Differentiate between Promises and Async/Await.
• What are your hobbies outside of work?
• Write a program that scores a tic-tac-toe board.
• Describe the usage of functions like forEach, Map, and Reduce in JavaScript.
• How would you describe "great" code?
• What is AJAX?
• What is your opinion on the latest React updates?
• How do you balance the need for innovation and the need for reliable code?
• What do you know about Redux?
• Create a multiplication function without using the multiplication operator.
• Describe the concept of closure.
• Differentiate between cookies and local storage.
• Write code using HTML and CSS for a US flag.
• What is responsive design?
• What was your last project, and what challenges did you face?
• Can you tell us about a project that you were passionate about from your experience?
• What are some improvements you'd suggest for our company website?
• How have you dealt with a team member not pulling their weight in the past?
• There are two very large numbers; each is so large that the only way to represent them is through an array of integers. Create a program with a function that multiplies them.
• Create a function that takes a string as input and returns all the unique letters present in it.
• Describe higher-order components (HOC) and their practical usage.
• How would you link your CSS and JS files to your HTML document?
• What was the last major challenge you faced in a program, and how did you overcome it?
• Create a function that calls an input function f every 50 milliseconds only.
• What is a CDN?
• Talk a bit about PureComponent and describe how you'd use it to your advantage.
• What can you bring to our company as a developer?