Yavashark

A small, embeddable and easily extendable JavaScript engine, built in Rust as a daily side project since March 17, 2024 — 950 consecutive days and over 4,200 commits by the time of its announcement.

It passes around 82% of the test262 test suite as of the October 2026 announcement, though the author notes many other features are still missing or half-implemented.

Modest today: it's mostly a tree-walking interpreter plus bytecode for async/await, with no hidden classes, inline caches, NaN-boxing, or optimized object layout. In early testing, a prototype with the planned new GC averaged about 3.5× V8's jitless mode across 19 microbenchmarks (beating it in every one, and beating JIT-enabled V8 in a few like exceptions and generators) — but the author cautions integration may bring slowdowns and V8-level raw compute is not the goal.