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Elm

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Description #

Elm is a functional language for front-end web development that compiles to JavaScript. It emphasizes simplicity, type safety, and maintainability, making it ideal for building reliable and fast single-page applications (SPAs).

History #

Elm was created by Evan Czaplicki in 2012 as part of his thesis at Harvard. It quickly gained a reputation for producing bug-free web apps, thanks to its no-runtime-errors promise and elegant architecture.

Key milestones:

  • Released in 2012 with a focus on functional UI programming
  • Introduced the Elm Architecture, which influenced frameworks like Redux
  • Rapid growth in the React ecosystem as a model for robust UI state handling
  • Now supported by a strong open-source community and used in production by startups and enterprises

Hello World #

module Main exposing (main)

import Browser
import Html exposing (text)

main =
    Browser.sandbox { init = (), update = \_ model -> model, view = \_ -> text "Hello, World!" }

How to Run #

Online: #

Locally: #

  1. Install Elm:
npm install -g elm

Create a file named Main.elm and paste the code

Compile and view in browser:

elm make Main.elm --output=index.html

Open index.html in your browser

Key Concepts #

  • Browser.sandbox — simple structure for front-end Elm apps
  • view — returns the HTML to display
  • update — updates the model based on messages
  • init — initial state of the app
  • No null or undefined — Elm replaces them with types like Maybe
  • Strong static types — errors caught at compile time
  • Pure functions — no side effects in functions
  • Immutability — all data is immutable by default
  • Elm Architecture — update-view-message model
  • Friendly compiler — known for readable and helpful error messages

Try It Online #

🔗 Try Elm Online
🔗 Ellie – Online Elm Editor
🔗 Replit – Elm

Fun Facts #

  • Elm compiles to JavaScript, but eliminates runtime errors
  • The Redux state management library was inspired by Elm
  • Elm’s compiler messages are widely praised as the best in the industry
  • Many Elm users report dramatically fewer bugs in production
  • Elm encourages no side effects, resulting in very stable UIs

Resources #

Updated on June 7, 2025

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