Prepared by: Ashish Misal
This guide is a comprehensive compilation of the most important interview questions for JavaScript developers. By mastering these questions, developers can showcase their understanding of JavaScript's unique paradigms, essential programming concepts, and the nuances of building scalable applications. These questions not only test technical knowledge but also evaluate a developer's ability to architect solutions and adapt to evolving software development trends.
JavaScript supports multiple programming paradigms, including:
- Object-Oriented Programming (OOP) with prototypal inheritance.
- Functional Programming (FP) using closures, first-class functions, and immutability.
Functional programming is a paradigm that treats computation as the evaluation of mathematical functions. It avoids shared state and mutable data, making code more predictable and easier to debug.
Key points:
- Pure functions and avoiding side-effects.
- Features in JavaScript: first-class functions, higher-order functions, and immutability.
- Classical Inheritance: Instances inherit from classes, creating hierarchical class taxonomies.
- Prototypal Inheritance: Instances inherit directly from other objects, allowing for more flexible object composition.
- Eliminates side-effects, shared state, and race conditions.
- Declarative style improves readability and refactoring.
- Easier to scale computation across multiple processors.
- Steeper learning curve due to academic notation and abstract concepts.
- Code can be harder to read for those unfamiliar with FP idioms.
- Intuitive and easy to understand for modeling real-world entities.
- Imperative style provides straightforward execution flow.
- Shared state can lead to unpredictable behavior.
- Tight coupling and hierarchies can make codebases brittle.
Rarely or almost never. Prefer object composition over inheritance to reduce coupling and improve flexibility.
- When you need to compose objects dynamically.
- When inheritance is required but without rigid class hierarchies.
It suggests assembling objects using smaller, reusable components instead of creating hierarchical taxonomies. This improves code flexibility and avoids pitfalls like the "gorilla-banana problem."
- Two-Way Data Binding: UI and model synchronize dynamically (e.g., Angular).
- One-Way Data Flow: Model is the single source of truth, and changes propagate in a single direction (e.g., React).
- Easier to implement cross-cutting concerns.
- Shared memory access is faster.
- Tightly coupled components.
- Difficult to scale or maintain as the application grows.
- Independent scalability and maintainability.
- Easier to recompose services for different use cases.
- Overhead of managing distributed services.
- Initial complexity in setting up cross-cutting concerns.
Asynchronous programming allows code execution to continue without waiting for time-consuming operations (e.g., network requests) to complete. JavaScript uses an event loop to handle asynchronous tasks, making it ideal for:
- User interface responsiveness.
- High-performance server-side applications.
Key concepts:
- Non-blocking I/O.
- Promises, async/await, and event-driven architecture.
These questions focus on essential concepts and architectural patterns in JavaScript, ensuring a developer's ability to design and implement scalable and maintainable applications. By preparing thoroughly, you can confidently tackle technical interviews and excel as a JavaScript developer.