WebAssembly Interview Questions and Answers for 10 years experience

1. What is WebAssembly (Wasm)?

   • Answer: WebAssembly is a binary instruction format for a stack-based virtual machine. It's designed as a portable target for compilation of high-level languages like C, C++, Rust, and Go, enabling near-native performance in web browsers and beyond. It's not a programming language itself, but rather a low-level bytecode that browsers can execute efficiently.

2. Explain the advantages of using WebAssembly over JavaScript.

   • Answer: WebAssembly offers significant performance improvements over JavaScript, especially for computationally intensive tasks. It allows for faster execution speeds due to its binary format and direct access to system resources. It also enables the reuse of existing C/C++ codebases, facilitating easier porting of legacy applications. Furthermore, it provides improved security through its sandboxed environment.

3. Describe the WebAssembly module lifecycle.

   • Answer: A WebAssembly module goes through several stages: compilation (from .wasm bytes to a module instance), instantiation (creating an instance of the module), execution (running the module's functions), and potentially garbage collection (when the module is no longer referenced).

4. What are the different WebAssembly memory models?

   • Answer: WebAssembly primarily uses a linear memory model, which is a contiguous array of bytes. This provides a shared memory space between WebAssembly and JavaScript. More advanced memory models, like shared memory for multithreading, are being developed.

5. Explain the concept of WebAssembly imports and exports.

   • Answer: WebAssembly modules can import functions, memories, tables, and globals from the host environment (usually JavaScript). They can also export functions, memories, tables, and globals, making them available to the host environment. This enables communication and interaction between WebAssembly and JavaScript code.

6. How do you handle errors in WebAssembly code?

   • Answer: Error handling in WebAssembly involves using exceptions (similar to try-catch blocks in other languages) or returning error codes from functions. JavaScript code interacting with WebAssembly can catch exceptions thrown by WebAssembly code.

7. What are WebAssembly tables and their use cases?

   • Answer: WebAssembly tables are arrays of function references. They are often used to implement indirect function calls, crucial for dynamic dispatch and features like virtual function tables in object-oriented programming.

8. Explain the role of the WebAssembly MVP (Minimum Viable Product).

   • Answer: The WebAssembly MVP represented the initial core features of WebAssembly, focusing on providing a basic, efficient execution environment. It laid the foundation for future development and additions.

9. Describe the different types of WebAssembly globals.

   • Answer: WebAssembly globals can have various numeric types (e.g., i32, i64, f32, f64) and can be mutable or immutable (const).

10. How can you debug WebAssembly code?

    • Answer: Debugging WebAssembly involves using browser developer tools (like Chrome DevTools), specialized WebAssembly debuggers, or source-level debuggers that map back to the high-level language used for compilation. Strategies include setting breakpoints, inspecting variables, and stepping through the code.

11. How does WebAssembly interact with the DOM?

    • Answer: WebAssembly itself doesn't directly interact with the DOM. It needs to communicate with JavaScript, which then manipulates the DOM. This usually involves passing data between WebAssembly and JavaScript functions.

12. What are some common use cases for WebAssembly?

    • Answer: WebAssembly is used for various purposes, including game development, image and video processing, virtual reality/augmented reality applications, scientific computing, and applications requiring high performance, such as CAD software or 3D modeling tools running in the browser.

13. Explain the concept of SIMD in WebAssembly.

    • Answer: SIMD (Single Instruction, Multiple Data) instructions allow WebAssembly to perform parallel operations on multiple data points simultaneously, significantly improving performance for vectorized computations.

14. Discuss the security considerations when using WebAssembly.

    • Answer: WebAssembly's sandboxed execution environment inherently enhances security. However, developers must still be mindful of potential vulnerabilities like buffer overflows and memory corruption, implementing proper input validation and memory management.

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