JavaScript Developer Interview Questions Guide

Introduction

Hiring the right JavaScript Developer is critical in the Information Technology (IT) sector. The role requires a mix of language fundamentals, modern tooling, and an ability to build maintainable client and server code.

This guide provides a structured set of screening-ready questions for basic, intermediate, and advanced levels, plus five pre-screening one-way video interview questions ideal for efficient candidate evaluation on ScreeningHive.

JavaScript Developer Interview Questions

Basic JavaScript Developer Interview Questions

• Explain the differences between var, let, and const in JavaScript.
• What is a closure and when would you use one?
• How does the JavaScript event loop work?
• What are the primary data types in JavaScript?
• Describe hoisting and give an example of its effect.
• What is the difference between == and ===?
• How do you add an event listener to a DOM element and remove it?
• Explain promises and provide a simple example of chaining them.

Intermediate JavaScript Developer Interview Questions

• Describe how you would debug an intermittent memory leak in a single page application.
• How would you handle asynchronous errors in a fetch request sequence?
• Explain how modules work in ES6 and when to favor named exports over default exports.
• Provide a strategy to improve web app performance for slow initial loads.
• How do you design state management between components in a client application?
• Give an example of cross-origin resource sharing issues and how you would resolve them.
• Describe testing approaches you use for JavaScript code, including unit and integration tests.
• How do you prevent common security issues such as XSS in a JavaScript application?
• Explain event delegation and when it is beneficial to implement it.
• Describe how bundlers like Webpack or Rollup affect development and production builds.

Advanced JavaScript Developer Interview Questions

• Explain JavaScript engine internals such as garbage collection and just-in-time compilation and their impact on performance.
• How would you design a large-scale front end to support multiple teams using micro-frontend techniques?
• Discuss server-side rendering versus client-side rendering and considerations for hydration.
• Describe strategies for optimizing runtime performance in a complex application with heavy DOM updates.
• How do you approach designing an API client that needs to handle rate limits, retries, and backoff?
• Explain how you would detect and mitigate memory leaks in long-running web applications.
• Describe the trade-offs between immutability and mutable state in application architecture.
• How do you evaluate and choose a framework or library for a new project?
• Explain how you would implement observability and metrics for a JavaScript application in production.
• Describe a time you led a technical migration or large refactor and how you managed risk and quality.

Pre-Screening Video Interview Questions for JavaScript Developer

These pre-screening interview questions are designed for one-way video interviews on ScreeningHive. They help assess communication, practical knowledge, problem solving, and cultural fit before live interviews.

1. Describe a recent JavaScript project you worked on and your specific contributions.

   This evaluates practical experience, role fit, and the candidate's ability to explain technical work clearly.

2. How do you stay current with JavaScript language updates and ecosystem changes?

   This assesses continuous learning habits and familiarity with modern best practices.

3. Provide a brief walkthrough of how you would debug a performance bottleneck in a web app.

   This reveals problem solving, familiarity with tools, and approach to performance optimization.

4. Explain how you would ensure code quality and maintainability in a team setting.

   This checks for experience with code review, testing, linting, and collaborative workflows.

5. Discuss a difficult bug you fixed and what you learned from resolving it.

   This probes troubleshooting skills, ownership, and the ability to learn from challenges.

Conclusion

These JavaScript Developer interview questions provide hiring teams and candidates with a clear, role-specific framework for evaluation. Using structured sets for basic, intermediate, and advanced levels helps match skills to job requirements.

ScreeningHive supports one-way video interviews to speed up candidate screening, standardize evaluations, and reduce time-to-hire. Incorporate these questions into your pre-screening and interview stages to improve consistency and hiring outcomes.