Installation

CDN and online playground

If you're new to JavaScript or just want a very simple setup to get your feet wet, you can get Mithril.js from a CDN:

<script src="https://unpkg.com/mithril/mithril.js"></script>

If you would like to try out mithril without setting up a local environment, you can easily use an online playground at flems.io/mithril.

npm

$ npm install mithril --save

TypeScript type definitions are available from DefinitelyTyped. They can be installed with:

$ npm install @types/mithril --save-dev

For example usage, to file issues or to discuss TypeScript related topics visit: https://github.com/MithrilJS/mithril.d.ts

Type definitions for pre-release versions of Mithril.js (on the next branch) align with the next branch of the types development repo. You can install these types with:

$ npm install -D MithrilJS/mithril.d.ts#next

Quick start with Webpack

Initialize the directory as an npm package
```
$ npm init --yes
```

install required tools

$ npm install mithril --save
$ npm install webpack webpack-cli --save-dev

Add a "start" entry to the scripts section in package.json.

{
 "...": "...",
 "scripts": {
     "start": "webpack ./src/index.js --output-path ./bin --watch"
 }
}

Create src/index.js file.

import m from "mithril";
m.render(document.body, "hello world");

create index.html

<!DOCTYPE html>
<body>
 <script src="bin/main.js"></script>
</body>

run bundler
```
$ npm start
```
open index.html in a browser

Optionally, you can include Mithril.js as a global variable using Webpack's provide plugin, to avoid including import m from "mithril" across a large number of files:

plugins: [
    new webpack.ProvidePlugin({m: "mithril"}),
    // ...
]

Then, you could remove the import line from step 4 (don't forget to restart Webpack if you ran it with --watch), and it will work just the same.

Step by step

For production-level projects, the recommended way of installing Mithril.js is to use npm.

npm is the default package manager that is bundled with Node.js. It is widely used as the package manager for both client-side and server-side libraries in the JavaScript ecosystem. Download and install Node; npm is bundled with that and installed alongside it.

To use Mithril.js via npm, go to your project folder, and run npm init --yes from the command line. This will create a file called package.json.

npm init --yes
# creates a file called package.json

Then, to install Mithril.js, run:

npm install mithril --save

This will create a folder called node_modules, and a mithril folder inside of it. It will also add an entry under dependencies in the package.json file

You are now ready to start using Mithril. The recommended way to structure code is to modularize it via CommonJS modules:

// index.js
var m = require("mithril")

m.render(document.body, "hello world")

Modularization is the practice of separating the code into files. Doing so makes it easier to find code, understand what code relies on what code, and test.

CommonJS is a de-facto standard for modularizing JavaScript code, and it's used by Node.js, as well as tools like Browserify and Webpack. It's a robust, battle-tested precursor to ES6 modules. Although the syntax for ES6 modules is specified in Ecmascript 6, the actual module loading mechanism is not. If you wish to use ES6 modules despite the non-standardized status of module loading, you can use tools like Rollup or Babel.

Most browser today do not natively support modularization systems (CommonJS or ES6), so modularized code must be bundled into a single JavaScript file before running in a client-side application.

A popular way for creating a bundle is to setup an npm script for Webpack. To install Webpack, run this from the command line:

npm install webpack webpack-cli --save-dev

Open the package.json that you created earlier, and add an entry to the scripts section:

{
    "name": "my-project",
    "scripts": {
        "start": "webpack src/index.js --output bin/app.js -d --watch"
    }
}

Remember this is a JSON file, so object key names such as "scripts" and "start" must be inside of double quotes.

The -d flag tells webpack to use development mode, which produces source maps for a better debugging experience.

The --watch flag tells webpack to watch the file system and automatically recreate app.js if file changes are detected.

Now you can run the script via npm start in your command line window. This looks up the webpack command in the npm path, reads index.js and creates a file called app.js which includes both Mithril.js and the hello world code above. If you want to run the webpack command directly from the command line, you need to either add node_modules/.bin to your PATH, or install webpack globally via npm install webpack -g. It's, however, recommended that you always install webpack locally and use npm scripts, to ensure builds are reproducible in different computers.

npm start

Now that you have created a bundle, you can then reference the bin/app.js file from an HTML file:

<html>
  <head>
    <title>Hello world</title>
  </head>
  <body>
    <script src="bin/app.js"></script>
  </body>
</html>

As you've seen above, importing a module in CommonJS is done via the require function. You can reference npm modules by their library names (e.g. require("mithril") or require("jquery")), and you can reference your own modules via relative paths minus the file extension (e.g. if you have a file called mycomponent.js in the same folder as the file you're importing to, you can import it by calling require("./mycomponent")).

To export a module, assign what you want to export to the special module.exports object:

// mycomponent.js
module.exports = {
    view: function() {return "hello from a module"}
}

In the index.js, you would then write this code to import that module:

// index.js
var m = require("mithril")

var MyComponent = require("./mycomponent")

m.mount(document.body, MyComponent)

Note that in this example, we're using m.mount, which wires up the component to Mithril.js' autoredraw system. In most applications, you will want to use m.mount (or m.route if your application has multiple screens) instead of m.render to take advantage of the autoredraw system, rather than re-rendering manually every time a change occurs.

Production build

If you open bin/app.js, you'll notice that the Webpack bundle is not minified, so this file is not ideal for a live application. To generate a minified file, open package.json and add a new npm script:

{
    "name": "my-project",
    "scripts": {
        "start": "webpack src/index.js --output bin/app.js -d --watch",
        "build": "webpack src/index.js --output bin/app.js -p",
    }
}

You can use hooks in your production environment to run the production build script automatically. Here's an example for Heroku:

{
    "name": "my-project",
    "scripts": {
        "start": "webpack -d --watch",
        "build": "webpack -p",
        "heroku-postbuild": "webpack -p"
    }
}

Alternate ways to use Mithril.js

Live reload development environment

Live reload is a feature where code changes automatically trigger the page to reload. Budo is one tool that enables live reloading.

# 1) install
npm install mithril --save
npm install budo -g

# 2) add this line into the scripts section in package.json
#    "scripts": {
#        "start": "budo --live --open index.js"
#    }

# 3) create an `index.js` file

# 4) run budo
npm start

The source file index.js will be compiled (bundled) and a browser window opens showing the result. Any changes in the source files will instantly get recompiled and the browser will refresh reflecting the changes.

Vanilla

If you don't have the ability to run a bundler script due to company security policies, there's an options to not use a module system at all:

<html>
  <head>
    <title>Hello world</title>
  </head>
  <body>
    <script src="https://unpkg.com/mithril/mithril.js"></script>
    <script src="index.js"></script>
  </body>
</html>

// index.js

// if a CommonJS environment is not detected, Mithril.js will be created in the global scope
m.render(document.body, "hello world")