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Elixir Phoenix with Typescript and React – December 2019 Edition

Alistair A. Israel
Learned programming (in BASIC) on a ZX Spectrum+. Dozens of years, platforms, and languages later, and still learning.
Updated on ・7 min read

"Great", you might say, "yet another article on how to set up Elixir, Phoenix and React!"

I myself have done this too many times over the past year or two, each time stumbling upon or rediscovering dozens of other guides and sample repositories, some still referencing outdated versions of Elixir (1.8.x), Phoenix (1.3.x), and React (pre-hooks).

So I finally decided to take it upon myself to write a definitive December 2019 (I would've wanted to call it "the 2020 Edition", but that'll have to wait for a month or two) guide to setting up Elixir, Phoenix, and React from scratch.

Let's jump right in.


This guide assumes you already have the following set up:

  • Elixir (1.9.4 or better)
  • npm (@6.11.3 as of this writing)
  • Docker (optional, for running PostgreSQL)

If you don't have Elixir (and Erlang) yet, I highly recommend asdf to manage Elixir/Erlang versions.

Install asdf according to your platform's instructions.


(If you're already experienced with Elixir Phoenix applications, you may wish to skip ahead to the Typescript and React parts.)

If you haven't already done so, let's install Phoenix following the Phoenix installation instructions. First we'll want to get the Hex package manager:

$ mix local.hex
Are you sure you want to install ""? [Yn] Y
* creating root/.mix/archives/hex-0.20.1

Then the Elixir Mix archive:

$ mix archive.install hex phx_new 1.4.11
Resolving Hex dependencies...
Dependency resolution completed:
  phx_new 1.4.11
* Getting phx_new (Hex package)
All dependencies are up to date
Compiling 10 files (.ex)
Generated phx_new app
Generated archive "phx_new-1.4.11.ez" with MIX_ENV=prod
Are you sure you want to install "phx_new-1.4.11.ez"? [Yn] Y
* creating /root/.mix/archives/phx_new-1.4.11

You can check if Phoenix installation went well using mix --version

$ mix --version
Phoenix v1.4.11

Generate the Phoenix app

$ mix hello_react --umbrella

This will generate an Elixir + Phoenix umbrella app named hello_react_umbrella in the current directory with the following directory structure:

├── apps
│   ├── hello_react
│   └── hello_react_web
├── config
└── deps

The two Elixir apps are /apps/hello_react and apps/hello_react_web.

Each app will its own dependency configuration, though the entire umbrella project will have a shared dependency library (in /deps) for all apps.

All child apps also share the same root configuration in the /config folder.

We start with an umbrella app because it makes it easier to organize code as the application gets bigger and more complex. Besides, we've found that it's easier to refactor an umbrella app project to a single app project than it is to go the other way around.

PostgreSQL, MySQL, or --no-ecto

Phoenix by default uses Postgres for its database.

If you want to use MySQL rather than Postgres, then you'll need to generate your Phoenix app using

mix hello_react --umbrella --database mysql

If you won't be needing a database or only wish to follow along without one, then create your Phoenix app using

mix hello_react --umbrella --no-ecto

The rest of this guide, however, assumes the default which is Postgres.

Docker Compose

Since we'll be needing a PostgreSQL server to run our Phoenix app, for local development and testing purposes we've found that using Docker, specifically, Docker Compose makes dealing with service dependencies a breeze.

Create the following docker-compose.yml in the project root:

version: "3"
    image: postgres:11.5
      - 5432:5432
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres
      POSTGRES_DB: hello_react_dev

Note that we configure PostgreSQL (using the POSTGRES_* environment variables) to work with the generated Phoenix app defaults.

Then, to run Postgres in the background you only need to go:

$ docker-compose up -d
Creating network "hello_react_umbrella_default" with the default driver
Creating hello_react_umbrella_postgres_1 ... done

Since Docker Compose is beyond the scope of this article, for other Docker Compose commands please just visit:

If you can't or don't want to use Docker & Docker Compose, you'll have to install PostgreSQL by hand on your local workstation. Make sure to configure it with the same defaults generated by mix, or, modify the respective config/*.exs files with the appropriate credentials.


Before we can run our Phoenix application, we need to initialise the generated CSS and Javascript assets.

Change directory do apps/hello_react_web/assets and from there, run npm install:

~/hello_react_umbrella/apps/hello_web/assets$ npm install


added 724 packages from 397 contributors and audited 7793 packages in 19.734s
found 0 vulnerabilities

Welcome to Phoenix!

At this point we should be able to run our Phoenix application. From the project root (you may wish to run this in a new terminal window or tab):

$ mix phx.server

Now if we visit http://localhost:4000 we should be able to see the familiar "Welcome to Phoenix!" page:

Welcome to Phoenix


We're ready to start adding Typescript to the frontend.

First, make sure we're back in apps/hello_react_web/assets/.

Add the Typescript libraries using:

$ npm install --save-dev typescript ts-loader source-map-loader @types/phoenix


Afterwards, let's ask Typescript to generate a default tsconfig.json for us:

$ ./node_modules/.bin/tsc --init
message TS6071: Successfully created a tsconfig.json file.

We need to change a few things from the Typescript defaults. Here's a minimal tsconfig.json with some of the necessary changes:

  "compilerOptions": {
    "target": "es5",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019' or 'ESNEXT'. */
    "module": "ESNext",                       /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
    "allowJs": true,                          /* Allow javascript files to be compiled. */
    "jsx": "react",                           /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
    "outDir": "./dist/",                      /* Redirect output structure to the directory. */
    "strict": true,                           /* Enable all strict type-checking options. */
    "esModuleInterop": true,                  /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */   
    "forceConsistentCasingInFileNames": true  /* Disallow inconsistently-cased references to the same file. */
  "exclude": [


Next, we'll need to tell Webpack to recognise .ts files along with .js files:

Open apps/hello_react_web/assets/webpack.config.js and change the first module rule to:

    rules: [
        test: /\.(j|t)s$/,
        exclude: /node_modules/,
        use: [
            loader: "babel-loader"
            loader: "ts-loader"

Additionally, add an outermost "resolve" key after "module" as follows:

  resolve: {
    extensions: [".ts", ".js"]


When we generated our Phoenix app, it created apps/hello_react_web/assets/js/app.js with an import css from "../css/app.css"; line.

This causes problems when that file is parsed by Typescript. You can see a lengthy discussion and several workarounds for this at this Stackoverflow question and on this page.

The simplest (though not the best) way to fix this before proceeding (so Webpack will continue to process our app.css) is to change that line to use require:

const _css = require("../css/app.css");

Since we don't actually use the variable (we only need it so Webpack can generate our app.css file properly), we prepend its name with an underscore to suppress the "unused variable" warning that Typescript would otherwise emit.

Welcome to Phoenix with Typescript!

To demonstrate Typescript in action, we'll create a new Typescript module apps/hello_react_web/assets/js/hello.ts:

function greet(name: string): string {
  return "Welcome to " + name + " with Typescript!";

export default greet;

Then, in assets/js/app.js add the following lines toward the end:

import greet from "./hello";

document.querySelector("section.phx-hero h1").innerHTML = greet("Phoenix");

Refresh the page at localhost:4000 and you should now see it say "Welcome to Phoenix with Typescript!".

Welcome to Phoenix with Typescript!


Let's go ahead and add React roughly following the guide at:

First we add the necessary packages:

$ npm install --save react react-dom
$ npm install --save-dev @types/react @types/react-dom

Once again we need to reconfigure webpack.config.js.

Then we tell Webpacker to recognize *.jsx and *.tsx files:

    rules: [
        test: /\.(j|t)sx?$/,
        exclude: /node_modules/,


  resolve: {
    extensions: [".ts", ".tsx", ".js", ".jsx"]

Our First Component

Save the following to apps/hello_react_web/assets/js/greeter.tsx:

import React from "react";

interface GreeterProps {
  name: string;

const Greeter: React.FC<GreeterProps> = (props: GreeterProps) => {
  const name =;
  return (
    <section className="phx-hero">
      <h1>Welcome to {name} with Typescript and React!</h1>
        A productive web framework that
        <br />
        does not compromise speed or maintainability.

export default Greeter;

Welcome to Phoenix with Typescript and React

Next, in apps/hello_react_web/lib/hello_react_web/templates/page/index.html.eex, remove the section:

<section class="phx-hero">
  <h1><%= gettext "Welcome to %{name}!", name: "Phoenix" %></h1>
  <p>A productive web framework that<br/>does not compromise speed or maintainability.</p>

And replace it with simply:

<div id="greeting"></div>

Then, in apps/hello_react_web/assets/js/app.js, replace the last few lines with:

import React from "react";
import ReactDOM from "react-dom";

import Greeter from "./greeter";

const greeting = document.getElementById("greeting");
ReactDOM.render(<Greeter name="Phoenix" />, greeting);

Finally (you may neeed to restart Phoenix and wait a sec for Webpack to compile everything), when we reload localhost:4000 we should see "Welcome to Phoenix with Typescript and React!`

"Welcome to Phoenix with Typescript and React!

Get the code

You can find a working repository for this article over at Github:

GitHub logo aisrael / elixir-phoenix-typescript-react

An example repository demonstrating Elixir 1.9.x with Phoenix 1.4.x, Typescript, and React

Discussion (6)

lucasprag profile image
Lucas Arantes

That's a great blog post, great job! However, It didn't work for me at the very end =/

I got this error:

Hash: 421850953aa4087426ac
Version: webpack 4.41.5
Time: 115ms
Built at: 04/02/2021 7:24:23 PM
                Asset       Size  Chunks             Chunk Names
       ../favicon.ico   1.23 KiB          [emitted]  
../images/phoenix.png   13.6 KiB          [emitted]  
        ../robots.txt  202 bytes          [emitted]  
               app.js   4.57 KiB     app  [emitted]  app
Entrypoint app = app.js
[0] multi ./js/app.js 28 bytes {app} [built]
[./js/app.js] 356 bytes {app} [built] [failed] [1 error]

ERROR in ./js/app.js 25:16
Module parse failed: Unexpected token (25:16)
You may need an appropriate loader to handle this file type, currently no loaders are configured to process this file. See
| const greeting = document.getElementById("root");
> ReactDOM.render(<Greeter name="Phoenix" />, greeting);
 @ multi ./js/app.js app[0]
Enter fullscreen mode Exit fullscreen mode

I believe it's because of the <Greeter which is React code in the app.js file.

I fixed it by moving the typescript/react code to a index.tsx file and then importing it inside the app.js file.


import React from "react";
import ReactDOM from "react-dom";
import Greeter from "./hello";

const greeting = document.getElementById("root");
ReactDOM.render(<Greeter name="Phoenix" />, greeting);
Enter fullscreen mode Exit fullscreen mode


const _css = require("../css/app.scss");
import "./index";
Enter fullscreen mode Exit fullscreen mode

This is how I fixed in case other people also face this error.

lucasprag profile image
Lucas Arantes

I also got another error, but I fixed by commenting out the "module": "ESNext" line of my tsconfig.json 👍

terenceponce profile image
Terence Ponce

Nice guide! How would you send data to the frontend in this scenario? Do you create an API that React will consume or are you going to still use Phoenix's offerings and just sprinkle React wherever needed?

aisrael profile image
Alistair A. Israel Author

Our tech stack of choice these days is GraphQL: absinthe-graphql on the Phoenix side, react-apollo on the browser-side, though if you're stuck with REST then mix phx.gen.json gets you most of the way there.

You just gave me great idea for a follow up article, though. Thanks!

maikroempagel profile image

Thx for the guide, really appreciate it!

One small error I found is that instead of

import greeting from "./hello";

in assets/js/app.js it should be

import greet from "./hello";

aisrael profile image
Alistair A. Israel Author

Ooh, thanks for catching that. Fixed now.