principletypescriptTip
WASM performance use cases and anti-patterns
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wasm performancewhen to use wasmcompute intensivecodeccompressionstartup cost
browserwasm
Problem
Developers use WebAssembly for tasks where it provides no benefit, or miss cases where it would dramatically improve performance.
Solution
Use WASM for: CPU-intensive computation (codecs, compression, crypto, simulation, parsers). Avoid WASM for: DOM manipulation, simple string processing, async I/O, tasks already fast in JS.
Why
WASM excels at tight compute loops with minimal JS boundary crossings. Each JS<->WASM call has overhead. If a function calls back to JS frequently, gains disappear.
Gotchas
- WASM startup (compilation + instantiation) adds latency — not suitable for one-time small tasks
- WASM does not have direct DOM access; UI code should stay in JS
- Calling WASM functions in a tight JS loop has per-call overhead — batch operations instead
- WASM is not automatically multi-threaded; use SharedArrayBuffer + Workers for parallelism
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