Small, baseline performant JavaScript runtime.
If you want to answer, how fast can JavaScript runtimes go? This is the place.
Elsa is "engine-agnostic". It has engine backends for:
- V8
- JavaScriptCore
- SpiderMonkey
- QuickJS
- Hermes
TypeScript stripping support available behind typescript feature flag using
swc. Typechecking done using stc.
When it first started out, Elsa was a fun project written in Go.
I was using just-js/spindle/crimson for baseline perf comparison when working on Deno. I wanted to benchmark against many many possibilities. Elsa is an attempt to write a cross-platform engine-agnostic fast JavaScript runtime.
Elsa is designed for:
-
Speed.
-
Size. Smallest configuration is 0.3MB.
-
Tons of compile time feature flags. Don't include things in the binary you don't need!
Ex: "I want to run a script in V8 that only uses FS apis, also don't want to type check but strip types":
cargo build --no-default-features --features "use_v8,fs,typescript" -
Easy to embed. Offers a Rust crate and C API (TODO).
Elsa is a hobby project. It does not intend to compete with major runtime.
To build Elsa, you need:
- Deno (>=1.28.3)
- Rust (>=1.66.0)
./build.ts debug # build debug. V8 without typescript support.
./build.ts release # build release.
./build.ts release-all # build release with all engine backends.
./build.ts release --features "use_quickjs,typescript,typecheck" # build release with quickjs and full TS support.
# ...You need python 3.9 (not 3.10) to build the spidermonkey backend.
# Warning: this may be destructive!
brew install [email protected]
cd $(dirname $(which python3.9))
rm -f python3 pip3
ln -s python3.9 python3
ln -s pip3.9 pip3- Note:
jscis not bundled but linked dynamically. This will change in the future and included it in the below table.
Without typescript support:
┌───────┬───────────┬───────────┐
│ (idx) │ feature │ size │
├───────┼───────────┼───────────┤
│ 0 │ "v8" │ "26.94MB" │
│ 2 │ "quickjs" │ "1.28MB" │
└───────┴───────────┴───────────┘
With typescript support:
┌───────┬───────────┬───────────┐
│ (idx) │ feature │ size │
├───────┼───────────┼───────────┤
│ 0 │ "v8" │ "31.96MB" │
│ 2 │ "quickjs" │ "6.30MB" │
└───────┴───────────┴───────────┘
Feel free to reach out if you are interested in contributing.
- No serde. It's a performance killer. Serializing objects is discouraged. If
you need to pass untyped complex data, use the engine's
Valuetype. - Typed data must always have inlined conversions using codegen in place.
- Everything should be behind a compile time feature flag.
MIT