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kbrw/reaxt

Use React template into your Elixir application for server rendering
Source code at GitHub https://github.com/kbrw/reaxt
kbrw/reaxt.json
{
  "createdAt": "2015-01-02T02:55:17Z",
  "defaultBranch": "master",
  "description": "Use React template into your Elixir application for server rendering",
  "fullName": "kbrw/reaxt",
  "homepage": "",
  "language": "Elixir",
  "name": "reaxt",
  "pushedAt": "2024-11-05T09:39:47Z",
  "stargazersCount": 373,
  "topics": [
    "elixir",
    "javascript",
    "react",
    "server-side-rendering",
    "webpack"
  ],
  "updatedAt": "2025-11-26T15:46:05Z",
  "url": "https://github.com/kbrw/reaxt"
}

Reaxt

Section titled “Reaxt”

Use your React components into your elixir application, using webpack compilation, so :

  • An isomorphic ready library (SEO/JS are now nice together), but with Elixir on the server side
  • Just a Library, with a minimum constraint about your application organization and layout :
    • use any javascript compiled language
    • use any javascript routing logic or library
    • you can use JS React rendered component only for parts of your webpage
  • Nice fluent dev workflow, with :
    • combined stacktrace : elixir | javascript
    • hot loading on both server and browser
    • NPM/Webpack as the only config for respectively dependencies/compilation
    • A cool UI to have an overview of your compiled javascript application
    • You do not have to think about the server side Javascript configuration, just write a webpack conf for the browser, and it is ready to use.

TODO List :

  • Handle Source map in server side for combined stacktrace generation
  • Add Source map in client side
  • Currently the compiler compile in parallel server entry and client entries, but server side compilation does not handle cacheable and slow down very much the compilation
  • handle css loader for reaxt/style loader, currently it is ignored in server side, which is a problem for URL remapping in CSS.

Usage

Section titled “Usage”

See https://github.com/awetzel/reaxt-example for a ready to use example application, but lets look into details and requirements.

In your mix.exs, add the dependency and the custom compiler for webpack:

  • Add the :reaxt dependency to your project.deps and application.applications
  • Add compilers: [:reaxt_webpack] ++ Mix.compilers to your project, (:reaxtWebpack for elixir < v1.0.3)

In your config/config.exs, link the reaxt application to the application containing the JS web app

  • config :reaxt,:otp_app,:yourapp

Create the good directory and file layout:

  • MIXROOT/web
  • MIXROOT/web/package.json containing your app NPM dependencies
  • MIXROOT/web/webpack.config.js containing only the client side logic, use “reaxt/style” instead of “style” loader to load your css. A typical output path is ../priv/static.
  • MIXROOT/web/components containing modules exporting React components

In your elixir code generating HTML :

  • add WebPack.header in the <head>
  • add a script with src /your/public/path/<%= WebPack.file_of(:entry_name) %>

Then render your server side HTML :

# if web/components/thefile exports the react component
Reaxt.render!(:thefile,%{it: "is", the: "props"})


# if web/components/thefile exports an object containing a react component
# at the key "component_key"


Reaxt.render!({:thefile,:component_key},%{it: "is", the: "props"})

The function return a %{html: html,css: css,js_render: js_render}, you have to add in the html :

  • the css <style><%= render.css %></style>
  • the html in an identified block (<div id="myblockid"><%= render.html %></div>)
  • the client side rendering call with <script><%= render.js_render %>("myblockid")</script>

For example, if you want a page entirely generated by the react component exported at web/components/app.js, then in your elixir web server, send :

EEx.eval_string("""
  <html>
  <head> <%= WebPack.header %>
    <style><%= render.css %></style>
  </head>
  <body>
    <div id="content"><%= render.html %></div>
    <script unsrc="/public/<%= WebPack.file_of(:main) %>"></script>
    <script><%= render.js_render %>("content")</script>
  </body>
  </html>
""",render: Reaxt.render!(:app,%{my: "props"}))

Finally, you have to serve files generated by webpack :

plug Plug.Static, at: "/public", from: :yourapp

Then iex -S mix and enjoy, but the best is to come.

Custom Plug : Live reloading and WebPack web UI

Section titled “Custom Plug : Live reloading and WebPack web UI”

When you serve files generated by webpack, use the plug WebPack.Plug.Static instead of Plug.Static, it contains an elixir implementation of webpack-dev-server, and a nice UI.

  if Mix.env == :dev do
    use Plug.Debugger
    plug WebPack.Plug.Static, at: "/public", from: :myweb
  else
    plug Plug.Static, at: "/public", from: :myweb
  end

Then go to http://yourhost/webpack to see a beautiful summary of your compiled js application.

Then configure in your application configuration :

  • config :reaxt,:hot,true to enable that:
    • server and client side JS will be compiled each time you change files
    • server side renderers will be restarted at each compilation
    • client browser page will be reloaded, a desktop notification will be triggered
    • The /webpack UI will be automatically reloaded if it is on your browser
  • config :reaxt,:hot,:client to enable the same hot loading, but with webpack module hot loading on browser to avoid full page reload
    • use the webpack loader react-hot-loader to load your component to enable automatic browser hot reloading of your components
    • the reaxt/style loader for your css enable hot reloading of your css

Dynamic Handler and customize rendering (useful with react-router)

Section titled “Dynamic Handler and customize rendering (useful with react-router)”

See a full example in reaxt-example

Reaxt provides facilities to easily customize the rendering process at the server and the client side : this is done by attaching reaxt_server_render and/or reaxt_client_render to the module or object referenced by the first argument of Reaxt.render!(.

  • reaxt_server_render(arg,render) will
    • take arg from the second argument of Reaxt.render,
    • have to execute render(component,param) when the wanting handler and props are determined. param is any stringifyable object passed to client rendering
  • reaxt_client_render(props,render,param) have to render the good selected component on the client side.
    • props is the initial props used in server rendering,
    • render is function you have to call to make the client react rendering
    • param is the deserialized version of the third parameter of the callback in reaxt_server_render

To understand how they work, let’s look at the default implementation of these functions (what happened when they are not implemented).

// default server rendering only take the exported module as the
// handler to render and the argument as the props
default_reaxt_server_render = function(arg,render){
  render(<this {...arg}/>,null)
}
// default client rendering only take the exported module as the
// handler to render, the param is ignored
default_reaxt_client_render = function(props,render,param){
  render(<this {...props}/>)
}

Now let’s see an example usage of these functions : react-router integration (Reaxt.render second argument is the Path): See a full example in reaxt-example

Reaxt.render!(:router_handler,full_path(conn))
var App = require("./app")
var Router = require("react-router")
var Routes = require("./routes")
module.exports = {
  reaxt_server_render: function(path,render){
    Router.run(Routes, path,function (Handler, state) {
      render(<Handler/>)
    })
  },
  reaxt_client_render: function(props,render){
    Router.run(Routes,Router.HistoryLocation,function(Handler,state){
      render(<Handler {...props}/>)
    })
  }
}

Error management

Section titled “Error management”

JS exceptions and stacktraces during rendering are converted into Elixir one with a fake stacktrace pointing to the generated javascript file.

This is really nice because you can see javascript stacktrace in the Plug.Debugger UI on exception.

Global Configuration

Section titled “Global Configuration”

You can define a term in Elixir using Application env global_config which will be available globally in the server and the client side with require('reaxt/config').

config :reaxt,:global_config, %{
  some_config1: "value1",
  some_config2: "value2"
}

This configuration is static once the :reaxt application has started. So if you want to change this configuration at runtime, you need to reload all :reaxt renderer with Reaxt.reload. Remember : this is a costly reload, do not use it to maintain a state at real time but only for configuration purpose.

Application.put_env :reaxt, :global_config, %{
  some_config1: "value3",
  some_config2: "value4"
}
Reaxt.reload

Then in your javascript component, you can use this config using :

require('reaxt/config').some_config1

Perfs and pool management

Section titled “Perfs and pool management”

The NodeJS renderers are managed in a pool (to obtain “multicore” JS rendering), so :

  • config :reaxt,:pool_size configure the number of worker running permanently
  • config :reaxt,:pool_max_overflow configure the maximum extension of the pool when query happens an it is full

A clever configuration could be :

config :reaxt,:pool_size, if(Mix.env == :dev, do: 1, else: 10)

For minification, remember that webpack compilation is launched by Mix, so you can use process.env.MIX_ENV in your webpack config.

{
  externals: { react: "React" },
  plugins: (function(){
    if(process.env.MIX_ENV == "prod")
      return [new webpack.optimize.UglifyJsPlugin({minimize: true})]
    else
      return []
  })()
}

CONTRIBUTING

Section titled “CONTRIBUTING”

Hi, and thank you for wanting to contribute. Please refer to the centralized informations available at: https://github.com/kbrw#contributing