GitHub Frontend Engineer Interview: Rounds, Questions and Preparation

What the job involves

Frontend Engineers build and maintain the user-facing parts of web applications, turning design mockups into responsive, accessible interfaces. At global tech companies, they collaborate with designers, backend engineers, and product managers to ship features that millions of users interact with daily. The role involves writing clean, testable code, optimizing performance, and ensuring cross-browser compatibility.

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` and `const`.

2. 2

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

   Explain diffing algorithm, reconciliation, and how it minimizes direct DOM manipulation for performance.

3. 3

   What are semantic HTML elements and why are they important?

   Give examples like `<header>`, `<nav>`, `<main>`, and discuss accessibility, SEO, and maintainability benefits.

4. 4

   Describe how you would make a web page responsive without using a framework.

   Mention media queries, flexible grids, relative units (%, rem, vw), and mobile-first approach.

Practical Scenarios

1. 5

   A page you built loads slowly. How would you diagnose and fix the issue?

   Use Lighthouse, check network waterfall, optimize images, code-split, lazy load, and minimize render-blocking resources.

2. 6

   You need to implement a feature that requires fetching data from an API and displaying it with loading and error states. Walk through your approach.

   Describe state management (useState/useEffect), conditional rendering, error boundaries, and maybe React Query or SWR.

3. 7

   How would you ensure your application is accessible to screen reader users?

   Discuss ARIA roles, semantic HTML, keyboard navigation, focus management, and testing with tools like axe or screen readers.

4. 8

   You are asked to refactor a large legacy jQuery codebase to React. What steps would you take?

   Suggest incremental migration, identifying components, writing tests, and using wrappers to run both side by side.

Behavioural and HR

1. 9

   Tell me about a time you received critical feedback on your code. How did you handle it?

   Show openness to feedback, focus on learning, and describe how you improved the code or process.

2. 10

   Describe a project where you had to collaborate with non-engineers (designers, PMs). How did you ensure smooth communication?

   Highlight empathy, clear documentation, regular syncs, and using tools like Figma or GitHub issues.

3. 11

   Why do you want to work as a frontend engineer at a global tech company?

   Connect personal passion for user experience with the company's scale and impact. Mention specific products or values.

4. 12

   How do you stay updated with frontend trends and best practices?

   Mention blogs, newsletters, open source contributions, side projects, and communities like GitHub or Dev.to.

Problem Solving and Coding

1. 13

   Write a function that debounces another function.

   Explain closure, setTimeout, clearTimeout, and use cases like search input or window resize.

2. 14

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

   Use reduce or a Map to accumulate groups. Discuss time complexity and immutability.

3. 15

   Implement a simple counter component in React that increments and decrements.

   Use useState, event handlers, and ensure no direct state mutation. Mention testing edge cases.

4. 16

   How would you find the first non-repeating character in a string?

   Use a hash map to count frequencies, then iterate to find first with count 1. Discuss O(n) time.