dartea is a compiler for the Elm language. It is written in OCaml. It takes Elm code and produces modern JavaScript.
The language is the same Elm. Same syntax, same types, same error messages, same Html library. The difference starts after the type checker.
The output is JavaScript as people write it today. ES modules. const and arrow functions. async and await. fetch and AbortSignal. One .mjs file per Elm module.
Dead code is removed across modules. A counter app compiles to about 2 KB.
If you need old browsers, run the output through any bundler with a target. There is nothing unusual in it.
dartea owns the Html library, the compiler and the runtime. So the compiler can see the shape of a view function.
The static part of a view becomes a DOM template. It is created once and cloned. The dynamic parts become holes with direct links to DOM nodes. On update the runtime looks at the values in the holes and writes only the ones that changed. There is no tree diff.
Elm values never change in place. So "did this value change" is one reference check. You get fine grained updates with no reactive runtime and no new syntax. Html.Lazy still works. You do not need it anymore.
We run js-framework-benchmark. The script bench/run.sh clones it, adds dartea as one more framework and starts the official runner. The other frameworks are the official implementations from that repository. Only the dartea program is ours.
Result. Weighted geometric mean of slowdowns: vanilla 1.00, Solid 1.12, Svelte 1.12, dartea 1.18, Elm 1.52, React 1.58.
Screenshot of the result page from that run. Apple M5, headless Chrome, August 30, 2026. This is my machine, not the official published table.
Task is an async function. It gets an AbortSignal. Http is fetch with a timeout signal. Cmd.batch starts all commands at once and delivers the messages in order. The Elm architecture stays as it is. Ports and subscriptions work as before.
The upstream TodoMVC runs without changes. A parity test checks module by module against Elm.
Ready: elm/core, elm/html, elm/browser with sandbox, element, document and application, elm/url, elm/json, elm/http without Bytes and File, part of elm/time.
Missing: Random, Process, Set, Array, packages from the Elm registry.
dartea make src/Main.elm --output index.html
dartea make src/Main.elm --output app.js
dartea make src
The first makes a page with the script inside. The second makes a script. The third makes one .mjs per module.
To build from source you need OCaml 5.4. Run dune build and dune test.
BSD 3-Clause.
dartea is an independent project. It is not part of the Elm project and Elm does not endorse it.
Some standard library modules come from elm/core, elm/html, elm/browser, elm/url and elm/http by Evan Czaplicki. LICENSE lists every such file. Compiled output includes dartea.LICENSE.txt only when one of those modules is in it.