Deno Interview Questions and Answers for 7 years experience

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Deno Interview Questions (7 Years Experience)

  1. What are the key differences between Deno and Node.js?

    • Answer: Deno uses V8 (like Node.js), but is built on TypeScript, utilizes a secure-by-default model with explicit permission grants, and employs ES modules instead of CommonJS modules. It also has built-in support for many features Node.js requires external packages for (e.g., testing, HTTP). Node.js has a larger community and ecosystem, offering more mature libraries and tools.

  2. Explain Deno's permission model. Why is it important?

    • Answer: Deno's permission model is crucial for security. Instead of granting broad access by default, Deno requires explicit permission flags for network access, file system access, environment variables, etc. This minimizes the risk of malicious code causing harm. Permissions are requested at runtime, providing more control and transparency.

  3. How does Deno handle modules? Compare this to Node.js.

    • Answer: Deno uses standard ES modules (import/export). This is a significant difference from Node.js which traditionally relies on CommonJS (require/module.exports). ES modules offer better tooling support, improved static analysis and easier code organization and maintainability.

  4. What are the benefits of using TypeScript with Deno?

    • Answer: TypeScript provides static typing which helps catch errors during development rather than runtime, improving code quality and reliability. It offers autocompletion and better refactoring capabilities in IDEs and enhances maintainability on larger projects.

  5. How can you test your Deno code?

    • Answer: Deno includes a built-in testing framework accessible via `Deno.test()`. This facilitates writing unit and integration tests directly within the Deno runtime. No external testing library is needed, simplifying the setup.

  6. Explain how to use `Deno.readTextFile()` and `Deno.writeTextFile()`.

    • Answer: `Deno.readTextFile(path)` asynchronously reads the contents of a file at the given path, returning a promise that resolves to a string. `Deno.writeTextFile(path, content)` asynchronously writes the given content to a file at the specified path, creating the file if it doesn't exist. Both require appropriate file system permissions.

  7. Describe Deno's standard library. Give examples of useful modules.

    • Answer: Deno offers a comprehensive standard library with modules for HTTP, file system interactions, encoding, and more. Examples include `std/http`, `std/fs`, `std/log`, `std/fmt`, and `std/testing`. These provide fundamental functionalities without relying on external dependencies.

  8. How does Deno handle dependencies? Contrast this with npm.

    • Answer: Deno doesn't use a centralized package manager like npm. Dependencies are imported directly via URLs or local file paths. This simplifies dependency management, avoiding complexities associated with package.json and node_modules. However, it requires careful management of URLs and version control.

  9. How can you improve the performance of a Deno application?

    • Answer: Performance optimization in Deno involves techniques like efficient use of asynchronous operations (async/await), minimizing I/O operations, using efficient data structures, and profiling the application to identify performance bottlenecks. Careful consideration of algorithm complexity is also essential.

  10. How would you handle errors in a Deno application?

    • Answer: Error handling in Deno typically involves using `try...catch` blocks to handle exceptions. For asynchronous operations, `.catch()` methods on promises are used. Custom error types can be defined for better organization and clarity. Logging errors to the console or a log file is also important for debugging and monitoring.

  11. [Question 11]

    • Answer: [Detailed Answer 11]

  12. [Question 12]

    • Answer: [Detailed Answer 12]

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