WebAssembly vs JavaScript – AP Hogeschool
A summary of my school project research comparing WebAssembly and JavaScript performance.
This blog post is a summary of my school project research comparing WebAssembly (Wasm) and JavaScript (JS). The purpose of the project was to understand how these two technologies perform for computationally intensive tasks in modern browsers and when it is best to use one over the other.
Why Compare WebAssembly and JavaScript?
JavaScript has been the standard language for web development for years. It is great for dynamic content, handling user interactions, and working with the DOM. However, it was not originally designed for heavy computations or complex algorithms.
WebAssembly, introduced in 2017, allows developers to run code compiled from languages like C, C++, or Rust in the browser at near-native speed. It works alongside JavaScript, making it possible to offload heavy tasks to Wasm while still handling the UI with JavaScript.
The Research
To compare performance, i tested three classical algorithms:
- Fibonacci Calculation – tests raw computation and recursion performance.
- Mandelbrot Rendering – tests graphics computation and canvas updates.
- Sieve of Eratosthenes – tests array manipulation, memory access, and algorithm efficiency.
Each algorithm was implemented in both JS and Wasm, then run multiple times in the same browser environment to measure execution time accurately.
Results Overview
| Algorithm | Input Example | JS Time (ms) | Wasm Time (ms) | Notes |
|---|---|---|---|---|
| Fibonacci (recursive) | n = 35 | 67.6 | 11.1 | Wasm is ~6x faster |
| Mandelbrot (canvas) | 500x500 pixels | 5.5 | 5.0 | Small advantage for Wasm |
| Sieve of Eratosthenes | n = 10,000,000 | 19.7 | 11.3 | Wasm faster, advantage decreases for very large n |
Key Observations
- WebAssembly excels at computation-heavy tasks like recursion, large array processing, and graphics calculations.
- JavaScript remains strong for tasks involving user interfaces, DOM manipulation, and logic that is less CPU-intensive.
- Performance gains with WebAssembly decrease as dataset sizes grow very large due to memory allocation limits and overhead in Wasm execution.
- A hybrid approach is often optimal: Wasm handles the heavy lifting, while JS manages UI and interactive components.
Practical Implications
WebAssembly is already used in many real-world applications:
- Games: Unity and Unreal Engine run complex 3D games in the browser.
- Image and video editing: Figma and Photoshop use Wasm for client-side processing.
- Machine learning: TensorFlow.js leverages Wasm for faster computation.
Meanwhile, JavaScript continues to dominate in areas like:
- Interactive web interfaces (React, Vue, Angular)
- Server-side applications (Node.js)
- Rapid prototyping and iterative development
Conclusion
This research shows that WebAssembly and JavaScript complement each other. Wasm is ideal for performance-critical parts of web applications, while JavaScript remains the best tool for handling the interface, events, and DOM-related tasks. Using both together allows developers to build fast, interactive, and efficient web applications.