How To Study for Frontend Interviews (2024) — All In One Guide

How To Study for Frontend Interviews (2024) — All In One Guide

Studying for frontend interviews can be quite challenging. Unlike general software engineering interviews that focus heavily on algorithmic questions, frontend interviews tend to focus more on real-world domain-specific questions related to HTML, CSS, JavaScript, and more.

We will guide you through the essential topics to study and prepare for in order to succeed in frontend engineering interviews at top tech companies such as Google, Meta, and Apple.

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Top Seven Frontend Interview Topics

1. Fundamental And Practical Javascript, Html, and CSS Knowledge
2. Javascript Trivia Questions
3. Basic Data Structure and Algorithmic Knowledge
4. Javascript Coding Questions
5. App Design Questions (Both Vanilla Javascript and React)
6. Frontend System Design
7. Behavioral Questions

1. Fundamental And Practical Javascript, Html, and CSS Knowledge

To excel in frontend interviews, you need a strong foundation in JavaScript, HTML, and CSS. While I cannot cover everything in detail within this article, I recommend studying the comprehensive resource javascript.info thoroughly. Some key areas to focus on include:

• Array methods (such as slice, splice, forEach, map, and reduce).
• Object methods for iteration and extracting keys/values.
• Understanding the differences between maps and sets, and the use cases of Symbols.
• String methods like slice, substring, indexOf, and includes.
• Primitives (e.g., NaN vs Null, strict equality checking, type conversion).
• Closures, “this” context, and the differences between call, apply, and bind.
• Object-oriented JavaScript and understanding prototypal inheritance.
• Functional programming concepts.
• Familiarity with various design patterns like MVC and MVVM, and their pros and cons.
• Promise, callback, async-await related concepts, polyfills of native JS function, JS working, rendering concepts.
• Additional questions can be found here.

2. Javascript Trivia Questions

Frontend interviews often include verbal trivia questions to assess your understanding of JavaScript concepts. Here are a few examples of common JavaScript trivia questions you may encounter:

1. What is closure, and how is it used?
2. What is the difference between .call() and .apply()?
3. Explain event delegation and how it differs from event bubbling.

All Trivia Questions can be found in the Frontend Knowledge Section.

3. Basic Data Structure and Algorithmic Knowledge

Although frontend interviews typically don’t heavily focus on algorithms, it’s crucial to have a solid understanding of basic data structures and algorithms. Brush up on the following topics:

1. Stacks and queues.
2. Basic tree traversal techniques.
3. Hashmaps and their applications.
4. Recursion and its use cases.
5. Memoization, caching.
6. Understanding Big O notation to analyze algorithm efficiency.

Having a solid grasp of these concepts will help you tackle any algorithmic questions that may arise during the interview process. All DS problems can be found here.

4. Javascript Coding Questions

Frontend interviews often involve coding questions that assess your ability to write JavaScript code. Some examples of coding questions you may encounter include:

1. Create a debounce function from scratch.
2. Implement throttling in JavaScript.
3. Build a promise from scratch.
4. Flatten an array
5. Traverse DOM tree
6. Build array.reduce, array.filter, array.map

Additional Coding Questions can be found here.

5. App Design Questions (Both Vanilla Javascript and React)

In frontend interviews, you are expected to demonstrate your ability to design and build applications using both Vanilla JavaScript and React. Practice building various components and features commonly found in web applications, including:

1. Todo app: Understand the core functionality of adding, deleting, and updating tasks.
2. Image carousel: Learn how to create a responsive image carousel with user interactions and transitions.
3. Fetching data from an API and rendering it dynamically in the user interface.
4. Creating tables with sorting and filtering functionality.
5. Implementing modals for displaying content on top of the main interface.
6. Building a star rating system with user input and display.
7. Developing checkboxes where selecting the parent also selects nested children.
8. Creating a progress bar to indicate the completion of a task.
9. Implementing auto-complete typeahead functionality.
10. Designing masonry-type layouts similar to Pinterest.
11. Building infinite scrolling applications.

Additional App Design Questions can be found here.

By gaining hands-on experience in building these features, you’ll be better prepared for app design questions in interviews.

6. Frontend System Design

System design interviews for frontend positions require considering various aspects of architecture, performance, and user experience. While I will provide separate in-depth articles and videos on frontend system design interviews, here are some high-level points to consider:

1. Gather all requirements for the system, including core features, mobile-first considerations, pagination support, etc.
2. Design the architecture and define responsibilities for each component.
3. Define the API data model and design the API itself, considering factors like pagination and the choice between GraphQL and REST.
4. Optimize the system’s performance at both the data layer (caching, memoization) and the render layer (bundling, image caching/minification).
5. Improve Time to Interactive (TTI) and explore AB testing to measure and enhance it.
6. Consider user experience aspects such as keyboard shortcuts, loading indicators, accessibility, error handling, server-driven UI, and observability/AB testing/tracking.

Additional System Design Questions can be found here.

Stay tuned for our separate articles and videos, where I will delve into frontend system design in detail, providing you with valuable insights and guidance.

7. Behavioral Questions

In addition to technical knowledge, behavioral questions play a significant role in frontend interviews. Here are some key tips to help you prepare:

1. Learn and practice the STAR answer format (Situation, Task, Action, Result) to structure your responses effectively.
2. Prepare answers to commonly asked behavioral questions, focusing on your experiences and accomplishments.
3. Showcase how your experiences align with the company’s culture and core values.
4. Try out mock behavioral interviews with friends or mentors to gain confidence in your responses.
5. Utilize structured courses or resources that offer guidance on answering behavioral questions effectively.

Among these, concepts like separation of concerns, the single-threaded non-blocking event loop, the distinction between call stack, event queue, and heap, as well as compile-time versus runtime type checking, and the notorious callback hell are pivotal. Let’s delve into each of these topics to help you gear up for your next frontend interview.

Preparing well for behavioral questions will allow you to effectively showcase your skills, experiences, and cultural fit during the interview process.

Bonus Material

1. Separation of Concerns

In the context of frontend development, the principle of Separation of Concerns (SoC) refers to the organization of code in a way that separates different functionalities and concerns into distinct sections. This principle is crucial for creating maintainable, scalable, and easily debuggable applications. For instance, in a web application, SoC is often implemented by separating the structure (HTML), presentation (CSS), and behavior (JavaScript) of the application.

• Interview Prep Tip: Understand how frameworks like React, Angular, or Vue enforce SoC through components, services, and directives. Be prepared to discuss how you’ve applied SoC in your projects to improve code quality and maintainability.

2. Single-thread, Non-blocking Event Loop

JavaScript is single-threaded, meaning it can only execute one task at a time. However, it is known for its non-blocking behavior, primarily due to the event loop mechanism. The event loop allows JavaScript to perform asynchronous operations such as API calls or timers without blocking the main thread, enabling a smooth user experience even in complex applications.

• Interview Prep Tip: Be ready to explain how the event loop works, including the roles of the call stack, task queue, and microtask queue. Discuss how this affects the performance and responsiveness of web applications.

3. Call Stack vs Event Queue vs Heap

Understanding the differences between the call stack, event queue, and heap is essential for any frontend developer:

• Call Stack: This is where the JavaScript engine tracks function execution. Each entry represents a function call. The stack operates on a LIFO (Last In, First Out) principle.
• Event Queue: Also known as the task queue, this is where asynchronous callbacks are placed, waiting to be executed once the call stack is empty.
• Heap: This is the memory space where objects are stored. It’s less structured compared to the stack but crucial for dynamic memory allocation.
• Interview Prep Tip: Be prepared to discuss how these components interact in the JavaScript runtime environment, particularly how asynchronous callbacks move from the event queue to the call stack.

4. Compile Time vs Runtime Type Checking

Type checking can occur at two stages: compile-time and runtime. Compile-time type checking, as seen in languages like TypeScript, occurs as the code is being compiled. Runtime type checking happens as the code is executed, which is more common in dynamically typed languages like JavaScript.

• Interview Prep Tip: Discuss the advantages of using TypeScript for compile-time type checking in large applications and how it can prevent certain types of runtime errors. Understand the trade-offs between flexibility and safety when it comes to type checking in frontend development.

5. Callback Hell

Callback hell, also known as “Pyramid of Doom,” refers to the heavily nested, hard-to-read code that arises when using multiple asynchronous callbacks. This pattern not only makes the code less readable but also harder to maintain and debug.

• Interview Prep Tip: Be familiar with strategies to avoid callback hell, such as using Promises or async/await syntax. Be able to refactor a nested callback code snippet into a cleaner, more maintainable structure during coding interviews.

In conclusion, studying for frontend engineering interviews requires a strong foundation in JavaScript, HTML, and CSS, familiarity with JavaScript trivia questions, understanding of basic data structures and algorithms, proficiency in solving JavaScript coding questions, hands-on experience in designing applications using both Vanilla JavaScript and React, knowledge of frontend system design principles, and effective preparation for behavioral questions. By dedicating time and effort to studying these topics and practicing your skills, you’ll be well-equipped to succeed in frontend engineering interviews and land your dream job at top tech companies.

Remember to utilize online resources, practice coding exercises, and seek out mock interview opportunities to further enhance your preparation. Best of luck on your frontend engineering interview journey in 2023!