JavaScript engines written in Nim

Bali is an experimental JavaScript engine implemented in Nim, with lexer, parser, ECMAScript execution work, and Test262 tracking. Sev adds host/runtime concerns on top of Bali; Ferus is an experimental Nim web-engine project that uses Bali. Mirage is related IR/bytecode work.

These projects are valuable for language-runtime, sandbox, DSL, and browser-engine research, but they are not production alternatives to QuickJS, Node.js, or V8. For embedding JavaScript in a production Nim application, prefer an established engine exposed through C FFI, such as QuickJS or Duktape.

Rust's Boa is more mature as an embeddable engine: it has bytecode/register-VM architecture, a dedicated GC, modular crates, and stronger ECMAScript-conformance work. Bali and Boa have different primary goals: Bali explores a Nim-native browser/JS stack, while Boa prioritizes an embeddable Rust engine.

Boa, Nova, and Deno

Do not group these as equivalent Rust JavaScript engines. Boa is an embeddable Rust engine with parser, AST, bytecode compiler, register VM, dedicated GC, and runtime crates. Nova is an in-progress Rust JavaScript/WASM engine. Deno has a Rust runtime, but its JavaScript engine is the C++ V8 engine.

Boa is ahead of Bali in embedding APIs, bytecode-VM maturity, and ECMAScript-conformance work. Neither Boa nor Bali should be treated as Node.js or npm-compatible by default. Choose Bali/Sev for Nim-native runtime, sandbox, DSL, and web-engine research; choose an established C-API engine such as QuickJS/Duktape for direct production embedding from Nim, or Boa when the embedding boundary naturally lives in Rust.