Connecting React with Phoenix

Questions / Help
,
1

I’ve been trying to connect React to my Phoenix project but continue to get an error. The error says

Error in ./assets/js/app.jsx
Module build failed (from ./node_modules/babel-loader/lib/index.js);
SyntaxError: path -> app.jsx

const HelloReact = () => {
  return <div>Hello World</div>;
}

error points to < in

I feel like this may be a babel problem. I decided to move package.json, webpack.config.js and .babelrc to the top level due to a recommended approach on a guide I was following. Was hoping to get a second look at eyes with how I’ve configured my React. Thank you for all the help.

My .babelrc looks like

{
"presets": ["@babel/preset-env", "@babel/preset-react"],
"plugins": ["@babel/plugin-proposal-class-properties", "@babel/plugin-proposal-object-rest-spread"]
}

As for my config file

module.exports = (env, options) => ({
 optimization: {
  minimizer: [
   new UglifyJSPlugin({ cache: true parallel: true, sourceMap: false }),
   new OptimizeCSSAssetsPlugin({})
  ]
 },
entry: {
  app: "./assets/js/app.jsx"
},
output: {
  filename: "app.js",
  path: path.resolve(__dirname, "priv/static/js")
},
module: {
  rules: [
   {
     test: /\.(js|jsx)$/,
     exclude: /node_modules/,
     use: {
       loader: "babel-loader"
     }
  },
  {
    test: /\.css$/,
    use: [MiniCSSExtractPlugin.loader, "css-loader"]
  }
 ]
},
plugins: [
   new MiniCssExtractPlugin({ filename: "../css/app.css"}),
   new CopyWebpackPlugin([{ from: "assets/static/", to: "../" }])
],
resolve: {
  extensions: ["*", ".js", ".jsx"]
}
});
2

Most likely a Babel problem indeed, as it seems it’s not transpiling JSX to JS.

The Babel configuration is always giving me headaches, and right now I am not really sure, but isn’t babel.config.js supposed to replace .babelrc? If I am right about that, your babel.config.js will take precedence, and it does not include necessary presets like @babel/preset-react. That might be what causes JSX not to be transpiled.

2 Likes
3

If you are new to react use the creat react app it works with npx and the guide can be found here.

Also this is very important https://reactjs.org/blog/2018/10/01/create-react-app-v2.html

4 
const HelloReact = () => {
  return <div>Hello World</div>;
}

Is that your file?

I think You miss this…

import React from 'react';

Even if it is not visible, You need to import React before using this code

<div>...</div>

because it uses React.createElement() under the hood

1 Like
5

Also can you post your package.json file to see what packages you installed?

6

Also this tutorial should offer you a complete introduction to react and babel config the right way.

1 Like
7

Hm I’ve been trying to look into babel.config.js and it doesn’t seem to be a requirement. I may be wrong but thank you for replying. Will continue to look about both files.

8

Thank you for replying. Actually, it isn’t my first time using React but every time I try to use it for a project, the initial setup is usually a headache when it comes to webpack. Thank you for providing those linkes. I will take a look especially the tutorial I hope will point me in the right direction. As for the packages I installed, it’s

{
  "repository": {},
  "license": "MIT",
  "scripts": {
    "deploy": "webpack --mode production",
    "watch": "webpack --mode development --watch"
  },
  "dependencies": {
    "@babel/plugin-proposal-class-properties": "^7.5.0",
    "@babel/plugin-proposal-object-rest-spread": "^7.5.4",
    "phoenix": "file:deps/phoenix",
    "phoenix_html": "file:deps/phoenix_html",
    "react-router-dom": "^5.0.1"
  },
  "devDependencies": {
    "@babel/core": "^7.5.4",
    "@babel/preset-env": "^7.5.4",
    "@babel/preset-react": "^7.0.0",
    "babel-loader": "^8.0.6",
    "copy-webpack-plugin": "^4.5.0",
    "css-loader": "^2.1.1",
    "mini-css-extract-plugin": "^0.4.0",
    "optimize-css-assets-webpack-plugin": "^5.0.3",
    "react": "^16.8.6",
    "react-dom": "^16.8.6",
    "uglifyjs-webpack-plugin": "^1.2.4",
    "webpack": "4.28.4",
    "webpack-cli": "^3.3.5"
  }
}
9

I apologize for not copying the code exactly as what I wrote. That is my part that has mislead you. The entire file looks like this

import css from "../css/app.css";
import "phoenix_html";
import React from "react";

import ReactDOM from "react-dom";

console.log("I'm getting hit");

const HelloReact = () => {

return <h1>Hello React!</h1>;

};

const root = document.getElementById("root");

ReactDOM.render(<HelloReact />, root);
10

I may be wrong, but isn’t the return block supposed to be wrapped with parens ie :

return (<div>Hello react</div>);

?

11

Ok You do import React…

This is how I did for a babel 7.4.3 and React 16.8

I use a babel.config.js with this inside

module.exports = api => {
  api.cache(true);

  const presets = [
    [
      "@babel/preset-env",
      {
        targets: {
          edge: "17",
          firefox: "60",
          chrome: "67",
          safari: "11.1",
        },
        useBuiltIns: "usage",
        corejs: '3.0.0',
      },
      "@babel/preset-react",
    ],
  ];
  
  const plugins = [

  ];

  return {
    presets,
    plugins
  };
}

I think I got this config on the babel site.

You may adapt for your usage.

In webpack.config.js, I have

      {
        test: /\.jsx?$/,
        include: SRC_PATH,
        exclude: /node_modules/,
        loader: 'babel-loader',
        options: {
          rootMode: "upward",
        },
      },

BTW, as a minor note… I put react, react-dom in dependencies, and all @babel… in devDependencies

12

What happens if you add the "@babel/preset-env" and "@babel/preset-react" presets to the babel.config.js, and remove .babelrc entirely?

It really looks to me like "@babel/preset-react" is just not applied, and you definitely do not need both a babel.config.js and a root .babelrc, so you can simplify your setup by only using the former.

13

It is not mandatory to use parens in that case :slight_smile:

14

I thought it was because the react component isn’t immediately closed and all the docs seem to wrap those in parens on the react website. Plus, I’ve been bitten by many weird syntax errors while mixing jsx and plain Javascript so I thought it was worth a try. But admittedly, I still don’t have a clear mental model about the jsx syntactic rules (even after having shipped a product that relies a lot on react and has the same configuration as op, yet somehow works).

15

Thank you! it seems like it was exactly what everyone has been saying especially @lucaong in regards to using babel.config.js instead of .babelrc

1 Like
16

You were 100% correct in this one. I didn’t remove .babelrc but made the file and copied what was added in @kokolegorille and it started to work. From what I found in the docs, it looks like babel is trying to look for babel.config.js file which is what was causing this problem.

1 Like
17

Glad we managed to help :slight_smile: :white_check_mark:

2 Likes
18

I do remember that upgrading to Babel 7 was painful :slight_smile:

19

In my opinion React is cool but weird. The reason being when you use syntactic sugar (I forgot which package helps with it) there is a lot of crazy things you can do. Technically we are writing it in a style but it’s being translated into something different. An example was when I had to bind every function I was making before but now just needing to name = () => {}

20

I’ve tagged your answer as the solution since you first brought it up and it was exactly what you said in regards to replacing .babelrc thank you :slight_smile:

1 Like