Looker India Frontend Engineer Interview: Rounds, Questions and Preparation

What the job involves

Frontend Engineers at global tech companies build and maintain user interfaces for web applications, ensuring they are responsive, accessible, and performant. They collaborate with designers, backend engineers, and product managers to translate requirements into high-quality code. Day to day involves writing JavaScript/TypeScript, using frameworks like React or Angular, debugging, and optimizing for speed and usability.

Role and Technical Knowledge

1. 1

   Explain the difference between let, const, and var in JavaScript.

   Cover scoping (block vs function), hoisting, and reassignment rules. Mention temporal dead zone for let/const.

2. 2

   How does the virtual DOM work in React, and why is it useful?

   Describe how React creates a lightweight copy of the real DOM, diffs it, and batches updates to minimize reflows. Highlight performance benefits.

3. 3

   What are the key differences between CSS Flexbox and Grid? When would you use each?

   Explain Flexbox for one-dimensional layouts and Grid for two-dimensional. Give examples like navigation bars vs. page layouts.

4. 4

   How do you ensure a web application is accessible (a11y)?

   Mention semantic HTML, ARIA roles, keyboard navigation, color contrast, and testing with screen readers.

Practical Scenarios

1. 5

   You need to build a dashboard that displays real-time data from multiple APIs. How would you architect the frontend?

   Discuss component structure, state management (e.g., Redux or Context), WebSockets or polling, error handling, and loading states.

2. 6

   A page is loading slowly. How would you diagnose and fix performance issues?

   Mention tools like Lighthouse, Chrome DevTools, code splitting, lazy loading, image optimization, and minimizing bundle size.

3. 7

   How would you handle a situation where a backend API is not ready but you need to build the UI?

   Suggest mocking data with tools like Mock Service Worker or JSON files, defining API contracts early, and using feature flags.

4. 8

   You need to implement a complex form with validation. What approach would you take?

   Discuss controlled components, form libraries like Formik or React Hook Form, validation schema (Yup), and error display.

Behavioural and HR

1. 9

   Tell me about a time you had to learn a new frontend technology quickly for a project.

   Use STAR method: describe the situation, the technology, how you learned it (docs, tutorials, mentors), and the outcome.

2. 10

   Describe a situation where you disagreed with a designer or backend engineer. How did you resolve it?

   Focus on communication, empathy, and finding a solution that balances user experience and technical constraints.

3. 11

   Why do you want to work as a Frontend Engineer at a global tech company like Looker India?

   Show passion for frontend, mention the company's products or culture, and align your career goals with their mission.

4. 12

   How do you prioritize tasks when you have multiple deadlines?

   Talk about using tools like Jira or Trello, communicating with stakeholders, and focusing on impact vs. effort.

Coding and Problem Solving

1. 13

   Write a function to debounce another function. Explain its use case.

   Implement a debounce that delays execution until after a specified wait time. Mention use in search input or resize events.

2. 14

   Given an array of objects, write code to group them by a property.

   Use reduce to create an object with keys as property values and arrays as grouped items. Discuss time complexity.

3. 15

   How would you implement a simple client-side router in vanilla JavaScript?

   Explain using hashchange or history API, listening to route changes, and rendering corresponding components.

4. 16

   Write a function to flatten a nested array without using Array.flat().

   Use recursion or reduce to concatenate nested arrays. Handle different depths and non-array elements.