Yavashark: I've Built a JavaScript Engine Every Day for 950 Days
A solo-built JavaScript engine that passes 82% of test262 after 4,200+ commits in 950 days.
Yavashark is an embeddable JavaScript engine built by one person, with a commit every day since March 17, 2024 — over 4,200 so far. It passes 82% of test262 and already runs Temporal, Intl, and even React with TypeScript through its CLI. It's a tree-walking interpreter without hidden classes, inline caches or NaN-boxing yet, so the author calls it 'blazingly fast slow' — honest about trading speed for correctness while those optimizations get built. Extending it is one Rust macro to bind a function into JavaScript.
What holds up
- +Passes 82% of test262 already, with Temporal and Intl support built in.
- +One Rust macro binds any function into JavaScript — easy to extend with custom native capabilities.
- +Runs real TypeScript and React (with react-dom) through its CLI, not just toy scripts.
Mind the limits
- −No inline caches, hidden classes or NaN-boxing yet — by the author's own admission, 'blazingly fast slow'.
- −Solo project, one contributor so far — depending on it means depending on one person's time.
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