D*****ital Interview Experience — Senior Frontend Engineer | Round 1

Overview

The first round of this senior frontend engineer interview focused heavily on technical proficiency. Following a brief introduction, the interviewer immediately began assessing the candidate's knowledge across a range of frontend topics. The assessment included theoretical questions, requests for comparative analysis, and practical coding challenges.

Interview Rounds

The initial round consisted of a series of technical questions and a code snippet analysis. The questions covered a wide array of topics, indicating a comprehensive evaluation of the candidate's frontend expertise.

Technical Questions:

• Difference between long polling and server-sent events. Which one is better and in what scenario?
• What is CORS and how does it work?
• How can CORS issues be resolved? Why doesn't Postman face CORS errors while browsers do?
• What are the benefits of using the CORS mechanism?
• A button click triggers a process that takes 5 minutes to compute. How would you prevent blocking the UI for the user?
• Explain various techniques to implement microfrontends.
• Implement loading of microfrontend on scrolling.
• How do you manage compatibility between microfrontend apps using different versions?
• What if one microfrontend is upgraded — how do you ensure compatibility with the others?
• What are Webpack plugins and what configurations are typically required?
• How would you handle race conditions that may occur during the loading of microfrontends?
• Explain prototype inheritance in JavaScript.
• Are classes the default behavior in JavaScript? How are they implemented?
• What are common frontend design patterns you've used or are familiar with?
• How can you reduce the bundle size of a frontend application?

Code Analysis:

The candidate was presented with the following JavaScript code snippet:

const arr = [1, 2, 3, 4, [1, 2, 3]];
const arr2 = [...arr];
arr[3] = 10;
arr[4][1] = 50;
console.log(arr);
console.log(arr2);

The candidate was then asked:

• How would you create a deep copy of nested objects or arrays? Can you write a polyfill for it?
• Share a real-life use case where closures are useful.
• What features or behaviors in JavaScript are built on closure principles?

Key Takeaways

This interview round emphasized a strong understanding of fundamental frontend concepts, including asynchronous communication, browser security (CORS), UI performance optimization, and JavaScript's core principles such as prototypal inheritance and closures. Knowledge of microfrontend architecture and related challenges like version compatibility and race condition handling was also evaluated. The ability to analyze code snippets and propose solutions for common programming problems was crucial.