Your First Developer Interview: A Complete Guide for Junior Engineers in 2025

Your first technical interview is intimidating. I remember mine—I spent three days preparing, convinced I'd be asked to implement a compiler or design Facebook's infrastructure. Instead, they asked me to explain the difference between let and var, build a simple todo list component, and talk about a project I'd built.

Here's what I wish someone had told me: junior interviews aren't about knowing everything. They're about demonstrating solid fundamentals, showing you can learn, and proving you'd be pleasant to work with. Let me walk you through what actually happens and how to prepare.

What Junior Interviews Actually Test

Companies hiring junior developers know you don't have years of experience. They're not expecting you to architect distributed systems or optimize database queries. Here's what they actually care about:

Do you understand the fundamentals?

For a frontend role: Can you explain what the DOM is? Do you understand how events work? Can you write basic HTML, CSS, and JavaScript?

For a backend role: Do you understand HTTP? Can you explain what a REST API is? Do you know basic database concepts?

For a full-stack role: A combination of both, but probably less depth in each area.

Can you solve simple problems?

You might be asked to write a function to reverse a string, filter an array, or find the largest number in a list. These aren't trick questions. They're checking if you can translate a problem into working code.

Can you learn and adapt?

When you get stuck, how do you respond? When they give you a hint, can you incorporate it? When they ask about something you don't know, can you make intelligent connections to things you do know?

Would you be pleasant to work with?

This is huge. Companies can teach you technical skills. They can't teach you to be a good communicator or a collaborative teammate. Being friendly, asking good questions, and handling feedback well matters as much as your code.

The Typical Junior Interview Process

Initial Screening (15-30 minutes)

Usually a phone or video call with a recruiter or hiring manager. They'll ask:

• Tell me about yourself
• Why are you interested in this role?
• What projects have you worked on?
• What's your experience with [relevant technology]?

This isn't deeply technical. They're checking basic communication skills and whether you meet minimum requirements. Be conversational, enthusiastic, and honest.

Technical Phone Screen (30-60 minutes)

A more technical conversation, often with a developer. Mix of conceptual questions and possibly simple coding.

Conceptual questions:

• "What's the difference between == and === in JavaScript?"
• "Explain what a promise is."
• "What's the box model in CSS?"

Simple coding (shared screen or collaborative editor):

• "Write a function that returns the sum of an array."
• "Create a simple component that displays a list of items."

Take-Home Assignment (2-6 hours)

Many companies give you a project to complete at home. Common examples:

• Build a weather app that fetches from an API
• Create a simple blog with a few pages
• Implement a todo list with add/remove functionality

They're evaluating:

• Can you build something that works?
• Is your code readable and organized?
• Do you follow instructions?
• Do you handle edge cases?

On-Site or Final Interview (2-4 hours)

Usually multiple rounds:

1. Coding Challenge (45-60 minutes): Live coding on a whiteboard or computer. Problems are typically straightforward: implement a search function, build a simple UI component, manipulate data structures.

2. Technical Discussion (30-45 minutes): Discussing your take-home project or past projects. Be ready to explain your decisions, discuss trade-offs, and potentially modify your code.

3. Behavioral Interview (30-45 minutes): Questions about how you work, handle challenges, learn new things. Not super technical, but important for culture fit.

4. Team Meet (15-30 minutes): Sometimes you'll meet potential teammates. This is mutual evaluation—they're seeing if they want to work with you, and you're seeing if you'd like working there.

For more on the behavioral portion, see our behavioral interview guide.

How to Prepare: The Practical Strategy

You probably have limited time to prepare. Here's how to use it effectively.

Week 1-2: Fundamentals Review

Review the core concepts for your role. Don't try to learn everything—focus on understanding fundamentals deeply.

For JavaScript/Frontend roles:

• Data types and how JavaScript handles them
• Arrays and objects: creation, manipulation, common methods
• Functions: regular functions vs arrow functions, scope, closures
• DOM manipulation: selecting elements, changing content, handling events
• Async JavaScript: callbacks, promises, async/await basics
• Basic CSS: selectors, box model, flexbox, positioning

For Backend/Full-Stack roles:

• HTTP methods (GET, POST, PUT, DELETE) and when to use each
• What REST APIs are and basic structure
• Database basics: what they are, basic SQL if relevant
• Authentication concepts (even if you haven't implemented it)
• How servers handle requests

Resources:

• MDN (Mozilla Developer Network) for JavaScript fundamentals
• freeCodeCamp for interactive learning
• The official docs for whatever framework you're interviewing for

Don't just read—actually write code. Create small examples. Run them. Break them. Fix them. This cements understanding way better than passive reading.

Week 3-4: Practice Coding Problems

Start with easy problems. Don't jump to medium or hard difficulty yet.

Sites for practice:

• LeetCode (filter for "Easy" problems)
• HackerRank
• Codewars (start at 7kyu or 8kyu)

Focus on:

• Array manipulation (filter, map, reduce)
• String operations
• Simple algorithms (finding max/min, reversing, sorting)
• Basic data structures (arrays, objects/hash maps)

Spend 30-60 minutes daily. Quality over quantity—solve 2-3 problems deeply rather than rushing through 10.

More importantly: practice explaining your solutions out loud. Pretend you're in an interview. Say what you're thinking. This feels ridiculous at first but is crucial for interviews.

For structured problem-solving preparation, check out our algorithms guide.

Week 5-6: Build Something

Build a small project from scratch. Ideas:

• Weather app using a free API
• Personal portfolio site
• Quiz app with multiple choice questions
• Simple blog with a few posts
• Calculator with a UI

This serves multiple purposes:

• Gives you something to talk about in interviews
• Helps you understand how pieces fit together
• Reveals gaps in your knowledge
• Provides a reference for reviewing your code

Deploy it somewhere (Netlify, Vercel, GitHub Pages). Having a live link makes a better impression than "it's on my laptop."

Week 7-8: Mock Interviews and Behavioral Prep

Do at least 2-3 mock interviews with friends, mentors, or platforms like Pramp. Practice:

• Explaining your thought process while coding
• Handling hints and feedback
• Managing time pressure

Also prepare answers to common behavioral questions:

• Tell me about yourself (2-minute version of your background)
• Why do you want to be a developer?
• Tell me about a project you're proud of
• Describe a challenge you overcame while learning to code
• How do you approach learning new technologies?

Use the STAR method: Situation, Task, Action, Result. Make your stories specific and concrete.

What to Expect During the Interview

The Coding Challenge

You'll likely solve 1-2 problems in 45-60 minutes. They'll probably start easy to warm up, then increase difficulty.

Example progression:

1. "Write a function that sums numbers in an array" (warm-up)
2. "Now modify it to sum only even numbers" (variation)
3. "What if the array contains nested arrays?" (complexity increase)

How to approach it:

1. Repeat the question: "So I need to write a function that takes an array and returns the sum of all even numbers?"

2. Ask clarifying questions: "Should I handle negative numbers?" "What should happen with an empty array?"

3. Explain your approach: "I'll iterate through the array, check if each number is even using modulo, and add it to a running sum."

4. Start coding: Use meaningful variable names. Add comments for tricky parts.

5. Test your code: Walk through an example. "With input [1,2,3,4], we'd get... 2 + 4 = 6."

6. Fix bugs: If something's wrong, say "Let me trace through this again..." and debug methodically.

The Technical Discussion

They'll ask about projects you've built or concepts you claim to know. Be ready to go deeper than surface level.

Bad answer: "I used React for this project."

Good answer: "I used React because I needed interactive components. This todo list uses useState to manage the list of items and useEffect to persist them to localStorage."

If they ask about something you don't know, don't fake it:

Bad: "Oh yeah, I know all about WebSockets." (when you don't)

Good: "I haven't used WebSockets specifically, but I understand they enable real-time two-way communication between client and server. I've used polling as a simpler alternative in my projects."

The Behavioral Questions

These feel less technical but are equally important. They're evaluating:

• Communication skills
• Ability to learn from experiences
• How you handle challenges
• Cultural fit

Example question: "Tell me about a time you got stuck on a problem."

Weak answer: "I get stuck sometimes but I usually figure it out."

Strong answer: "When building my weather app, I couldn't get the API data to display. I spent an hour getting frustrated before I actually read the API documentation carefully and realized I was accessing the wrong property in the response object. That taught me to read documentation thoroughly before assuming something is broken."

For comprehensive preparation on these questions, see our behavioral interview guide.

Common Junior Developer Interview Questions

JavaScript/Frontend:

• What's the difference between let, const, and var?
• Explain how this works in JavaScript
• What are promises and why do we use them?
• How do you handle events in the DOM?
• Explain the CSS box model
• What's the difference between inline, block, and inline-block?
• How does flexbox work?

See our JavaScript interview guide for deeper preparation.

React (if applicable):

• What are components?
• What's the difference between state and props?
• What are hooks and when do you use them?
• How do you handle forms in React?

For React-specific preparation, check out our React interview guide.

General Programming:

• What's the difference between an array and an object?
• How do you reverse a string?
• Write a function to check if a number is even
• How do you remove duplicates from an array?

Backend (if applicable):

• What's a REST API?
• What's the difference between GET and POST?
• What are HTTP status codes and what do they mean?
• What's the difference between authentication and authorization?

For backend roles, see our Node.js interview guide.

The Day of the Interview

Technical Setup (for remote interviews)

Test everything 30 minutes before:

• Internet connection stable?
• Audio and video working?
• Screen sharing functional?
• Editor or IDE ready?
• Water nearby?

For comprehensive remote interview tips, see our remote interview guide.

Mental Preparation

You're going to be nervous. That's normal. Even experienced developers get nervous in interviews.

Some things that help:

• Review your projects the morning of
• Don't cram new material the day of
• Arrive/join 5-10 minutes early
• Take deep breaths before starting
• Remember that interviewers want you to succeed

During the Interview

Communicate constantly. Don't code in silence. Explain what you're thinking.

Ask questions. If something's unclear, ask. If you're stuck, ask for a hint.

Be honest. If you don't know something, say so. Better to admit a gap than to BS your way through.

Stay positive. Even if you mess up, keep going. I've seen candidates recover from bad starts and get offers.

Be pleasant. Smile. Be friendly. Show you'd be nice to work with.

What If You Don't Know Something?

You will definitely be asked about something you don't know. This is guaranteed. How you handle it matters more than knowing everything.

Bad responses:

• Complete silence
• "I don't know" with nothing else
• Making up an answer
• Getting defensive

Good responses:

• "I haven't used that specifically, but I understand it's similar to [related concept]. Can you tell me more about it?"
• "I'm not familiar with that. How does it work?"
• "I know the basics but haven't gone deep. My understanding is [what you do know]. Is that on the right track?"

This shows honesty, curiosity, and ability to connect new concepts to existing knowledge.

After the Interview

Send a Thank You Email

Within 24 hours, send a brief email to your interviewer(s):

"Thank you for taking the time to interview me today. I enjoyed discussing [specific thing you talked about] and learning more about [company/team]. I'm excited about the possibility of contributing to [specific project or goal]. Please let me know if you need any additional information."

Keep it short, genuine, and specific.

Reflect on What Happened

While it's fresh, write down:

• What questions were asked?
• What did you answer well?
• Where did you struggle?
• What would you do differently?

This helps you improve for the next interview (whether with this company or another).

Don't Obsess

You did your best. The outcome is partly out of your control. Sometimes you interview well and don't get the offer because there was a candidate with more experience. Sometimes you feel like you bombed it but get the offer anyway.

Apply to multiple companies. Keep studying. Keep building. Each interview makes you better at interviewing.

If You Get Rejected

Rejection is part of the process. Every developer, including the ones at top companies, has been rejected multiple times.

Ask for feedback: "Thank you for considering me. If possible, I'd appreciate any feedback on areas where I could improve."

Many companies won't give detailed feedback, but it's always worth asking.

Identify patterns: If you're consistently struggling with the same type of question (algorithm problems, JavaScript fundamentals, behavioral questions), that tells you where to focus your prep.

Keep going: Every interview is practice. You're building a skill. The 10th interview will go better than the first.

For guidance on avoiding common pitfalls, see our interview mistakes guide.

Final Thoughts

Your first developer interview is nerve-wracking, but remember:

• Companies hiring juniors expect junior-level knowledge
• They know you're still learning
• They're evaluating potential and fundamentals, not expertise
• Communication and attitude matter as much as technical skills

Prepare the fundamentals, practice coding problems, build something you're proud of, and be ready to explain your thinking. That's the formula.

You won't know everything. You'll make mistakes. You might blank on questions you know the answer to. That's all normal and okay.

The developers interviewing you were once exactly where you are. They remember being nervous junior candidates. Most of them want to help you succeed.

Now go review those fundamentals, practice talking through problems out loud, and get ready to show what you can do. You've got this.