This Project Is Deprecated

React Hot Loader 3 is on the horizon, and you can try it today (boilerplate branch, upgrade example). It fixes some long-standing issues with both React Hot Loader and React Transform, and is intended as a replacement for both. The docs are not there yet, but they will be added before the final release. For now, this commit is a good reference.

react-transform-hmr

A React Transform that enables hot reloading React classes using Hot Module Replacement API. Hot module replacement is supported natively by Webpack and available in Browserify with browserify-hmr.

🚧🚧🚧🚧🚧

This is highly experimental tech. If you’re enthusiastic about hot reloading, by all means, give it a try, but don’t bet your project on it. Either of the technologies it relies upon may change drastically or get deprecated any day. You’ve been warned 😉 .

This technology exists to prototype next-generation React developer experience. Please don’t use it blindly if you don’t know the underlying technologies well. Otherwise you are likely to get disillusioned with JavaScript tooling.

No effort went into making this user-friendly yet. The goal is to eventually kill this technology in favor of less hacky technologies baked into React. These projects are not long term.

Installation

First, install the Babel plugin:

npm install --save-dev babel-plugin-react-transform

Then, install the transform:

npm install --save-dev react-transform-hmr

React

Edit your .babelrc to include a plugin configuration for react-transform. It contains array of the transforms you want to use:

{
  "presets": ["es2015", "stage-0"],
  "env": {
    // only enable it when process.env.NODE_ENV is 'development' or undefined
    "development": {
      "plugins": [["react-transform", {
        "transforms": [{
          "transform": "react-transform-hmr",
          // if you use React Native, pass "react-native" instead:
          "imports": ["react"],
          // this is important for Webpack HMR:
          "locals": ["module"]
        }]
        // note: you can put more transforms into array
        // this is just one of them!
      }]]
    }
  }
}

Make sure you process files with babel-loader, and that you don’t use React Hot Loader (it’s not needed with this transform).

It is up to you to ensure that the transform is not enabled when you compile the app in production mode. The easiest way to do this is to put React Transform configuration inside env.development in .babelrc and ensure you’re calling babel with NODE_ENV=production. See babelrc documentation for more details about using env option.

Warning! This doesn't currently work for stateless functional components that were introduced in React 0.14!

React Native

This transform enables hot reloading when used together with React Native Webpack Server. However note that you should not use .babelrc to configure it with React Native. Otherwise you’ll get Uncaught SyntaxError: Unexpected reserved word in ActivityIndicatorIOS.ios.js.

There are two problems why .babelrc doesn’t work well in React Native:

Changes in it aren’t picked up by packager’s aggressive caching.
Another unknown problem causes import generated by babel-plugin-react-transform to not be compiled into a require call.

Until we have better .babelrc support in React Native, you should configure React Transform together with babel-loader:

var fs = require('fs');
var path = require('path');
var webpack = require('webpack');

var config = {
  debug: true,

  devtool: 'source-map',

  entry: {
    'index.ios': ['./src/main.js'],
  },

  output: {
    path: path.resolve(__dirname, 'build'),
    filename: '[name].js',
  },

  module: {
    loaders: [{
      test: /\.js$/,
      exclude: /node_modules/,
      loader: 'babel',
      query: {
        stage: 0,
        plugins: []
      }
    }]
  },

  plugins: []
};

// Hot mode
if (process.env.HOT) {
  config.devtool = 'eval';
  config.entry['index.ios'].unshift('react-native-webpack-server/hot/entry');
  config.entry['index.ios'].unshift('webpack/hot/only-dev-server');
  config.entry['index.ios'].unshift('webpack-dev-server/client?http://localhost:8082');
  config.output.publicPath = 'http://localhost:8082/';
  config.plugins.unshift(new webpack.HotModuleReplacementPlugin());

  // Note: enabling React Transform and React Transform HMR:
  config.module.loaders[0].query.plugins.push([
    'react-transform', {
      transforms: [{
        transform : 'react-transform-hmr',
        imports   : ['react'],
        locals    : ['module']
      }]
    }
  ]);
}

if (process.env.NODE_ENV === 'production') {
  config.plugins.push(new webpack.optimize.OccurrenceOrderPlugin());
  config.plugins.push(new webpack.optimize.UglifyJsPlugin());
}

module.exports = config;

See React Native Webpack Server examples for details.

License

MIT

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