What is a .elm file?
Elm Source File · Code and data · Evan Czaplicki · 2012
An .elm file is Elm source code, a purely functional language that compiles to JavaScript for building web front ends. Its compiler is famous for friendly error messages and for ruling out runtime exceptions.
What is a .elm file used for?
Elm takes the Haskell family of ideas and aims them squarely at the browser: no null, no undefined, and if an Elm program compiles it essentially cannot throw a runtime exception in practice.
The Elm Architecture (model, update, view) that structures every Elm app inspired Redux and much of modern front-end state management. The files are plain text.
How to open a .elm file
The .elm format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list. For a step-by-step walkthrough, see how to open a .elm file.
Windows
- VS Code (Elm extension)
- any text editor
macOS
- VS Code (Elm extension)
- any text editor
Linux
- VS Code (Elm extension)
- any text editor
How to convert a .elm file
You can convert a .elm file to js (compiled) using a conversion tool or the export menu of an app that opens it.
.elm file signature (magic bytes)
Programs recognise a .elm file by the bytes at the start of the file, not by its name. These are the signatures for Elm.
| Hex signature | Offset | Note |
|---|---|---|
| (no fixed signature) | 0 | plain text; no fixed magic bytes |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .elm file?
An .elm file is Elm source code, a purely functional language that compiles to JavaScript for building web front ends. Its compiler is famous for friendly error messages and for ruling out runtime exceptions.
How do I run an .elm file?
Install Elm and run elm reactor for a quick dev server, or elm make src/Main.elm to compile it to JavaScript or HTML you open in a browser.
Does Elm really have no runtime exceptions?
In practice, yes. The compiler forces every case (no null or undefined), so the classic JavaScript crashes cannot occur in pure Elm code.
What is the Elm Architecture?
A pattern of model, update and view that structures every Elm app. It predates and inspired Redux-style state management in JavaScript.
Related formats
Sources
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