# japgolly/scalajs-react

Facebook's React on Scala.JS

Repository: https://github.com/japgolly/scalajs-react
Canonical: https://ross.abutalabs.com/products/scalajs-react
Homepage: https://japgolly.github.io/scalajs-react/
Language: Scala
License: Apache-2.0
License Family: permissive
Topics: scala, react, reactjs, scalajs, fp, functional-programming, router
Last push: 2026-07-13T06:23:38+00:00

## Health v2 (maintenance only)
Score: 82/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 92, release rhythm 60, longevity 100
- inputs: {"age_days": 4444, "days_push": 51, "days_rel": 106, "gap_med": 107, "n_releases_24m": 4}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1657, forks 230 (observed 2026-08-28T04:05:18.182398+00:00)

## What it is
A Scala.js library that provides type-safe, Scala-friendly bindings for Facebook's React, with opt-in functional programming support via Cats, Cats Effect, and Monocle. It includes extra modules for routing, testing utilities, and performance management.

## Use cases
- build a React web app in Scala
- write type-safe React components with Scala.js
- use React hooks from Scala
- add client-side routing to a Scala.js frontend
- test React components in Scala
- do server-side rendering of React on the JVM
- use Cats Effect with React in Scala.js

## When to choose
- you are a Scala developer building a web frontend with React
- you want strong static typing and functional programming idioms over React
- you need React SSR from the JVM in a Scala stack

## When to avoid
- your team writes JavaScript or TypeScript rather than Scala
- you need a non-React frontend framework
- you are not using Scala.js in your build

## Facets
- artifact type: library
- maturity: active
- function: frontend-framework, ui-components, routing, testing, ssr
- domain: web-development, frontend
- platform: jvm, browser
- tags: scalajs, react, type-safe, cats-effect, hooks, fp, functional-programming, web-server

## Member repositories
- japgolly/scalajs-react (main) score 82

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:18.182398+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 2026-08-30T03:44:47.027711+00:00, confidence not recorded.
  - readme: https://github.com/japgolly/scalajs-react (fetched 2026-08-28T04:05:18.182398+00:00, sha cc42e4a96c88)
  - homepage: https://japgolly.github.io/scalajs-react/ (fetched 2026-08-29T11:17:20.370948+00:00, sha 44136fa355b3)
- Data as of 2026-08-30T08:39:29.467469+00:00.