Compile the numeric code you already test — no rewrite, no second toolchain.
No runtime, no GC, tiny output.
JZ compiles the numeric JavaScript you already test into native-grade WASM.
Valid JZ is valid JS. The same source remains your JS implementation and fallback, or compiles to sandboxed, portable .wasm. No rewrite, runtime, GC, or type annotations; auto-SIMD and deterministic output.
| Good for | Not for |
|---|---|
| DSP, audio, synthesis | UI, DOM, the frontend |
| Image, video, pixels | Serving HTTP, hot I/O |
| Simulation, physics, games | I/O-bound orchestration |
| Parsers, codecs, compression | Dynamic, polymorphic, OOP |
| Scientific, numeric, ML | Security crypto, big-ints |
| Hashing, checksums, RNG | Glue, plumbing, orchestration |
A minimal modern functional JS subset — no dynamic constructs or reflection. The jzify layer lowers legacy patterns, generators, and async/await.
let x = 0.5, Float32Array, an array index, a loop counter. JZ infers it instead of turning the file into another language. Ambiguous values take a slower, always-correct dynamic path.AssemblyScript is a TypeScript dialect — can’t run in a JS engine. Porffor chases the whole JS spec that affects performance and cannot compile itself yet.
Rust, Go, and C are excellent when a rewrite and second toolchain make sense. JZ is for the hot path you want to keep in JavaScript: one source, one test suite, a JS fallback, and comparable WASM or native performance.
The performance bar is uncompromising: on the cross-target corpus, the same source runs over 2× faster than V8 and Rust→WASM at near-native speed (geomean; per-case numbers and every loss are on the bench page). JZ auto-vectorizes where the Rust/C→WASM paths do not. A rival win remains a bug to close, not an exception to hide.
If you hit a slow case, report it →
jz → wasm2c → clang -O3 produces a standalone native binary. See full pipeline →.
jz.wasm, and CI passes self-compiled build the full test suite. 
It’s experimental (pre-1.0) — ABI can still shift.
But real code already ships on it: color-space v3 builds its precompiled 27-space WASM backend with JZ.
CI gates the full suite, test262, the bench, and the self-compile. A fuzzer diffs every kernel against the same source in V8.
And the exit is free: valid JZ is valid JS — drop the compile step and the same file keeps running.
jz kernel.js) or the API (compile()) produces a plain .wasm you load like any other module. Setup & options →Find it useful?
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