# lukehaas/RunJS

RunJS is a JavaScript playground for macOS, Windows and Linux. Write code with instant feedback and access to Node.js and browser APIs.

Repository: https://github.com/lukehaas/RunJS
Canonical: https://ross.abutalabs.com/products/runjs
Homepage: https://runjs.app
License Family: other
Topics: javascript, runjs, javascript-editor, electron, electron-app, electron-application, desktop-application, desktop-app, nodejs, typescript, playground, linux, macos, windows
Last push: 2026-07-13T08:37:59+00:00

## Health v2 (maintenance only)
Score: 94/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 92, release rhythm 92, longevity 100
- inputs: {"age_days": 2880, "days_push": 51, "days_rel": 57, "gap_med": 10, "n_releases_24m": 14}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2167, forks 53 (observed 2026-08-28T04:06:21.421223+00:00)

## What it is
RunJS is a desktop JavaScript and TypeScript playground for macOS, Windows, and Linux that runs code as you type with instant results. It provides built-in Node.js and browser environments, npm package installation, snippet libraries, and AI-assisted code generation without any project setup.

## Use cases
- experiment with an npm package without setting up a project
- learn new JavaScript or TypeScript syntax with instant feedback
- prototype a function in isolation before adding it to a codebase
- quickly transform JSON, CSV, or log data
- test API endpoints with fetch and inspect responses
- sketch React components, SVGs, or canvas animations
- run one-off scripts and calculations
- teach or learn JavaScript with a fast feedback loop

## When to choose
- you want a no-setup scratchpad for JS/TS experiments on your desktop
- you need both Node.js and browser APIs in one tool
- you're learning or teaching JavaScript and want instant evaluation
- you want to quickly test regexes, APIs, or libraries

## When to avoid
- you need a full IDE or project-based development workflow
- you need a free open-source tool (RunJS uses a paid license)
- you work primarily in languages other than JavaScript/TypeScript
- you need collaborative or browser-based sharing of snippets

## Facets
- artifact type: application
- maturity: active
- function: editor, developer-tools, cli
- domain: developer-tools, web-development, programming-languages, education
- platform: windows
- tags: javascript-playground, typescript, scratchpad, code-experimentation, npm-packages, snippet-library, prototyping, learning-tool, macos, linux, desktop, electron, nodejs

## Member repositories
- lukehaas/RunJS (main) score 94

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:06:21.421223+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 2026-08-30T02:49:32.150837+00:00, confidence not recorded.
  - readme: https://github.com/lukehaas/RunJS (fetched 2026-08-28T04:06:21.421223+00:00, sha f7274e534b03)
  - homepage: https://runjs.app (fetched 2026-08-29T10:30:08.770278+00:00, sha 616d17eda75b)
  - site_page: https://runjs.app/docs (fetched 2026-08-29T10:30:08.781621+00:00, sha 2285dba218b8)
  - site_page: https://runjs.app/about (fetched 2026-08-29T10:30:08.785024+00:00, sha 7e177a35654d)
  - site_page: https://runjs.app/buy (fetched 2026-08-29T10:30:08.779664+00:00, sha 74db0e3bfa4f)
  - site_page: https://runjs.app/releases (fetched 2026-08-29T10:30:08.783351+00:00, sha 0937c5baf78b)
  - site_page: https://runjs.app/faq (fetched 2026-08-29T10:30:08.786668+00:00, sha 022b4ac0b83c)
- Data as of 2026-08-30T08:39:29.467469+00:00.