experimental javascript runner

Run the same script on wildly different engines.

o- is a tiny multi-engine JavaScript runner with a shared bootstrap layer. It lets you compare SpiderMonkey, JavaScriptCore, and V8 behind one interface without flattening everything into the same boring developer experience.

Open the docs Compare engines

One script, multiple enginesShared jstd bootstrapColor-formatted runtime errorsDocs-first developer flow

$ o- run index.js
12586269025

$ cat ~/.config/o-/toolchain
v8

$ o- toolchain add spidermonkey
$ o- toolchain add javascriptcore

Execution Error: JavaScript exception is pending
--> index.js
 | console.log(fib(50))

SpiderMonkey

backend

fast bootstrap, unstable teardown

JavaScriptCore

backend

clean host callbacks, shared jstd surface

V8

backend

stable default runner, fresh isolate per run