WebAssembly Interview Questions and Answers for freshers
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What is WebAssembly?
- Answer: WebAssembly (Wasm) is a binary instruction format for a stack-based virtual machine. It's designed as a portable compilation target for programming languages like C, C++, Rust, and Go, enabling them to run in web browsers with near-native performance. It's not a programming language itself, but rather a low-level code format that browsers can efficiently execute.
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What are the key advantages of using WebAssembly?
- Answer: Key advantages include significantly improved performance compared to JavaScript for computationally intensive tasks, better security due to its sandboxed execution environment, and the ability to reuse existing codebases written in other languages.
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How does WebAssembly interact with JavaScript?
- Answer: WebAssembly modules can import and export JavaScript functions, allowing seamless interoperability. JavaScript can call Wasm functions, and Wasm can call JavaScript functions, enabling a hybrid approach where complex computations are handled by Wasm and the user interface and other aspects are managed by JavaScript.
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Explain the WebAssembly memory model.
- Answer: WebAssembly uses a linear memory model, essentially a large contiguous array of bytes. This memory is shared between the Wasm module and the JavaScript environment. Access to memory is managed carefully to prevent security vulnerabilities.
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What are WebAssembly modules?
- Answer: WebAssembly modules are self-contained units of code. They are compiled from source code (e.g., C++, Rust) into a binary format (.wasm) that can be loaded and executed by a WebAssembly runtime, typically within a web browser.
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Describe the different WebAssembly value types.
- Answer: WebAssembly has several value types: i32 (32-bit integer), i64 (64-bit integer), f32 (32-bit float), f64 (64-bit float), and anyref (a reference type that handles references to other objects). These types define the data manipulated within WebAssembly functions.
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What is the role of the WebAssembly runtime?
- Answer: The WebAssembly runtime is responsible for loading, validating, compiling (if necessary – some runtimes use ahead-of-time compilation), and executing WebAssembly modules. It provides the necessary environment, including memory management and interaction with the host environment (typically JavaScript).
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How is WebAssembly compiled?
- Answer: Source code in languages like C++, Rust, or Go is compiled into a WebAssembly binary using a compiler toolchain (e.g., Emscripten for C/C++). This binary (.wasm file) can then be loaded and executed by a WebAssembly runtime.
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Explain the concept of WebAssembly imports and exports.
- Answer: WebAssembly modules can import functions or memory from the host environment (usually JavaScript) and export functions or memory that can be accessed by the host. This allows for communication and data sharing between the Wasm module and the surrounding JavaScript code.
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What are the security implications of using WebAssembly?
- Answer: WebAssembly's sandboxed execution environment helps to mitigate security risks. However, careful consideration is still needed, especially regarding memory management and interactions with the host environment. Vulnerabilities can still exist in the Wasm code itself or in the JavaScript code that interacts with it.
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What is the difference between WebAssembly and JavaScript?
- Answer: WebAssembly is designed for performance and is typically compiled from lower-level languages, resulting in near-native speed for computationally intensive tasks. JavaScript is interpreted and generally slower for such tasks, but is more versatile for general-purpose web development and has a larger ecosystem.
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What are some common use cases for WebAssembly?
- Answer: Common use cases include high-performance games, image and video editing, scientific computing, virtual and augmented reality applications, and other tasks where performance is critical.
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How can you debug WebAssembly code?
- Answer: Debugging WebAssembly can be done using browser developer tools (like Chrome DevTools), which often provide support for inspecting Wasm memory, call stacks, and stepping through Wasm code. Source maps can help link the Wasm code back to the original source code for easier debugging.
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Explain the concept of WebAssembly tables.
- Answer: WebAssembly tables are arrays of function references. They are used to allow indirect function calls, where the function to be called is determined at runtime. This is useful for implementing features like polymorphism or dynamic dispatch.
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What is the role of the `WebAssembly.instantiate()` function?
- Answer: The `WebAssembly.instantiate()` function is used to load and instantiate a WebAssembly module from its binary representation (a .wasm file or array buffer). It returns a promise that resolves with an object containing the module's exports.
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What are some tools used for developing WebAssembly applications?
- Answer: Popular tools include Emscripten (for compiling C/C++ to Wasm), Binaryen (an optimizing compiler infrastructure for Wasm), and various language-specific compilers and toolchains for languages like Rust and Go.
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What are the limitations of WebAssembly?
- Answer: WebAssembly currently lacks direct access to certain browser APIs, although this is gradually improving. The debugging experience can sometimes be more challenging compared to JavaScript debugging. Also, the compilation process can add complexity to the development workflow.
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Explain the concept of garbage collection in WebAssembly.
- Answer: WebAssembly itself doesn't have built-in garbage collection. Memory management is typically handled either manually (requiring careful allocation and deallocation) or by relying on the garbage collection capabilities of the host language (like JavaScript).
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