# jterrace/js.js

js.js: A JavaScript JavaScript interpreter

Repository: https://github.com/jterrace/js.js
Canonical: https://ross.abutalabs.com/products/jterrace-jsjs
Language: JavaScript
License: NOASSERTION
License Family: other
Last push: 2022-02-19T20:23:41+00:00

## Health v2 (maintenance only)
Score: 32/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 0, release rhythm 35, longevity 100
- inputs: {"age_days": 5452, "days_push": 1656, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases, no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1082, forks 59 (observed 2026-08-28T04:03:30.915070+00:00)

## What it is
js.js is a JavaScript interpreter written in JavaScript, created by compiling SpiderMonkey to LLVM and translating it with Emscripten. It exposes a JSAPI-style wrapper so scripts can evaluate and run JavaScript code inside a browser or Node.js environment.

## Use cases
- run untrusted javascript in a sandboxed interpreter inside the browser
- evaluate javascript code from within a javascript application
- embed a separate javascript execution context in node
- build an in-browser javascript playground or REPL
- execute user-supplied scripts safely without eval

## When to choose
- you need to run JavaScript code isolated from the host page's real JS environment
- you want a self-contained interpreter that works in browser and Node.js
- you're experimenting with interpreter-in-interpreter techniques or teaching

## When to avoid
- you need fast execution - it's roughly 200x slower than native SpiderMonkey
- you need a small dependency - the compiled build is ~3MB (594KB gzipped)
- you need an actively maintained project - it dates from 2012 with no recent development
- you just want to evaluate trusted code - native eval or Function is far simpler

## Facets
- artifact type: library
- maturity: abandoned
- function: interpreter, compiler, developer-tools
- domain: programming-languages, compilers, developer-tools, web-development
- platform: browser, wasm
- tags: javascript-interpreter, spidermonkey, emscripten, transpilation, sandboxing, nodejs, javascript

## Member repositories
- jterrace/js.js (main) score 32

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:03:30.915070+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T06:51:16.151700+00:00, confidence not recorded.
  - readme: https://github.com/jterrace/js.js (fetched 2026-08-28T04:03:30.915070+00:00, sha ceee470b7cbf)
- Data as of 2026-08-30T08:39:29.467469+00:00.