whatisgithub

What is moon?

kbrsh/moon — explained in plain English

Analysis updated 2026-06-26

★ 5,959JavaScriptAudience · developerComplexity · 2/5LicenseSetup · easy

In one sentence

Tiny 2KB JavaScript library for building reactive web user interfaces using functional programming, where the UI is described as a function of data and updates automatically when the data changes.

Mindmap

mindmap
  root((moon))
    What it does
      UI rendering
      Functional design
      Reactive updates
    Features
      2KB after compression
      Fast rendering
      Driver-based design
    Licensing
      MIT license
      Free commercial use
    Use cases
      Lightweight web UIs
      Functional web apps
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Code map

Detail Auto

An interactive map of this repo's files and how they connect — its source is parsed live in your browser. Click Visualize to build it.

filefunction / class

What do people build with it?

USE CASE 1

Build a lightweight reactive web UI without pulling in a large framework like React or Vue.

USE CASE 2

Create a single-page app with automatically updating views using Moon's functional data-to-view approach.

USE CASE 3

Add interactivity to a web page with a 2KB script that loads faster than any major framework alternative.

What is it built with?

JavaScript

How does it compare?

kbrsh/moonjakiestfu/snap.jscuckoosandbox/cuckoo
Stars5,9595,9575,955
LanguageJavaScriptJavaScriptJavaScript
Setup difficultyeasyeasyhard
Complexity2/52/54/5
Audiencedeveloperdeveloperops devops

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · easy Time to first run · 30min

Full API documentation is on moonjs.org, the README is sparse and serves mainly as a brief introduction.

Use freely for any purpose including commercial use as long as you keep the copyright notice.

So what is it?

Moon is a small JavaScript library for building user interfaces in a web browser. It is designed around functional programming principles, meaning the UI is described as a function of data rather than through direct manipulation of the page. When your data changes, Moon figures out what needs to update and re-renders accordingly. The library's main selling points are its tiny size, 2 kilobytes after compression, and its rendering speed. The README describes a driver-based design, where different concerns like the view layer and state management are separated into distinct drivers, though the documentation site at moonjs.org is the place to find the full API details. The README itself is sparse and points to the site for usage guidance. Moon is written in JavaScript and available under the MIT license, which permits free commercial and personal use. The project was created and is maintained by Kabir Shah as an open source effort, supported through Patreon donations.

Copy-paste prompts

Prompt 1
Show me a minimal Moon app that renders a counter button and increments the count when clicked, using Moon's driver-based state management.
Prompt 2
How do I structure a Moon application with multiple views that each subscribe to different parts of the shared state?
Prompt 3
I want to build a small to-do list with Moon. Show me the data definition, the view function, and how to handle adding and removing items.
Prompt 4
Compare Moon's driver architecture to React hooks, how would I translate a useEffect data-fetch into Moon's equivalent pattern?

Frequently asked questions

What is moon?

Tiny 2KB JavaScript library for building reactive web user interfaces using functional programming, where the UI is described as a function of data and updates automatically when the data changes.

What language is moon written in?

Mainly JavaScript. The stack also includes JavaScript.

What license does moon use?

Use freely for any purpose including commercial use as long as you keep the copyright notice.

How hard is moon to set up?

Setup difficulty is rated easy, with roughly 30min to a first successful run.

Who is moon for?

Mainly developer.

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