Haxe externs for Mithril (JS MVC framework)
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Mithril for Haxe

Mithril is a small, yet great javascript MVC framework that is faster and more flexible than most others. Here's the Haxe version for Mithril 1.0+, with some useful extra features thanks to macros and the type inference.


Standard procedure: haxelib install mithril and then -lib mithril in your .hxml file.

How to use

Mithril has a great introduction on its website and an astounding amount of documentation, so I'll only highlight what you need to get started with the Haxe version here.

Implement the Mithril interface

Because Javascript is so dynamic and Haxe is strongly typed, the balance between flexibility and compiler safety can be difficult. When using Mithril, you will create components that will be used together with the Mithril API. For these objects you should implement the Mithril interface. Here's an example of a Mithril component:

import mithril.M;

class TodoComponent implements Mithril
    var todos : Array<Todo>;

    public function new(todos) {
        this.todos = todos;

    // When implementing Mithril, the last m() expression 
    // or Array of m(), is returned automatically.
    public function view() {
        m("div", [
            m("h1", "To do"),
            m("table", todos.map(function(todo) {
                m("tr", [
                    m("td", m("input[type=checkbox]", { 
                        onclick: function(e) todo.done = e.target.checked,
                        checked: todo.done
                    m("td", todo.description)
    // Program entry point
    static function main() {
        var todos = [
            new Todo("Learn Haxe"),
            new Todo("??"),
            new Todo("Profit!")
        M.mount(js.Browser.document.body, new TodoComponent(todos));

class Todo
    public var done : Bool = false;
    public var description : String;

    public function new(description) {
        this.description = description;

A few API differences

  • Use M, not m! import mithril.M;, then use M instead of m for the whole API. As you see above, the only exception is when using m(), you can use that without prefixing with M.
  • The route methods are available by a simple translation: M.route.link for example, becomes M.routeLink.

"this" is slightly different

Because of the slight mismatch between Haxe classes and the classless Mithril structure, an important difference is that in lifecycle methods, this points to vnode.tag instead of vnode.state. Otherwise this would have pointed to another object when inside instance methods.

This is usually nothing you have to worry about if you're using Haxe classes for your components and state. In that case this will work just normally.

Haxe examples

This repo has some examples that can be interesting to test. Clone it, open a prompt in the directory and run:

haxelib install mithril

Then select one of the following:

Some small apps

A collection of two demo apps, available on the Mithril site.

  1. haxe client.hxml
  2. nekotools server -d bin
  3. Open http://localhost:2000/ in a browser.


A simple, although incomplete, e-commerce site to demonstrate the power of Mithril.

  1. haxe webshop.hxml
  2. nekotools server -d bin/webshop
  3. Open http://localhost:2000/ in a browser.

Live demo here: http://ciscoheat.github.io/webshop

From scratch

If you prefer a bare-bones example (doesn't require cloning), create the following two files and follow the instructions below:


<!doctype html>
<script src="https://unpkg.com/mithril@1.0.0/mithril.js"></script>
<script src="example.js"></script>


import mithril.M;

class User
    public var name : String;

    public function new(name) {
        this.name = name;

class Example implements Mithril
    var user : User;

    public function new() {
        this.user = new User("Thorin Oakenshield");     

    public function view() [
        // Display an input field
        m('input', {
            // Updates the model on input
            oninput: function(e) user.name = e.target.value,

            // The redraw triggered by the oninput event will update
            // the input field value from the model automatically
            value: user.name
        // Display a div with class .user and some style
        m('.user', {style: {margin: "15px"}}, user.name)

    // Program entry point
    static function main() {
        M.mount(js.Browser.document.body, new Example());

Compile and run with:

  1. haxe -lib mithril -js example.js -main Example
  2. Open index.html in a browser.

Server side - All targets

The rendering part of Mithril has been ported to Haxe, so you can now enjoy writing Mithril templates, and have them rendered to HTML anywhere. Here's a class to get you started:

import mithril.MithrilNodeRender;
import mithril.M.m;

class Main {
    static function main() {
        var view = m("ul", [
            m("li", "item 1"),
            m("li", "item 2"),

        // <ul><li>item 1</li><li>item 2</li></ul>
        Sys.println(new MithrilNodeRender().render(view)); 

Server side - Node.js & isomorphism

Without too much hassle, it's possible to render a Mithril component/view serverside on Node.js. Run the following in the repo directory:

  1. npm install
  2. haxelib install hxnodejs
  3. haxe server.hxml
  4. cd bin

Example 1: Simple rendering

node server.js outputs a simple HTML rendering example.

Example 2: Isomorphic code

node server.js server

Starts a server on http://localhost:2000 that executes the same code on server and client. The server generates the HTML so the page is perceived to load quickly and search engines can index it, then the client enables the functionality.

Example 3: Cross-platform rendering

As a bonus, a Neko version of Example 1 will also be compiled. Test it with

neko server.n

The MithrilNodeRender is tested with travix and should work on all targets.

Finally, if you're using Node.js, you can install and use Mithril from npm instead of the Haxe port. To do that, define -D mithril-native.

Feedback please!

Feedback is always welcome! Open an issue and give me a piece of your mind. :)