Error when I tried to upgrade from webpack3 to webpack4 - reactjs

Question

I'm getting this below error when I upgraded my project from webpack 3.x to webpack 4.0.0
ERROR in multi script-loader!jquery/dist/jquery.min.js script-loader!foundation-sites/dist/js/foundation.min.js eventsource-polyfill webpack-hot-middleware/client?reload=true ./src/index.jsx
Module not found: Error: Can't resolve 'babel-loader' in 'C:\projects\rebasing\uisrc'
# multi script-loader!jquery/dist/jquery.min.js script-loader!foundation-sites/dist/js/foundation.min.js eventsource-polyfill webpack-hot-middleware/client?reload=true ./src/index.jsx
The rules configurations is as shown below in config file
rules: [
{
test: /\.(jsx?)$/,
use: 'babel-loader',
exclude: /node_modules/,
},
]
Package.json have following libraries
"devDependencies": {
"babel-cli": "6.26.0",
"babel-core": "6.8.0",
"babel-eslint": "7.0.0",
"babel-loader": "7.1.5",
"babel-preset-es2015": "6.6.0",
"babel-preset-react": "6.5.0",
"babel-preset-react-hmre": "1.1.1",
"babel-preset-stage-0": "6.5.0",
"babel-preset-stage-2": "6.17.0",
"babel-register": "6.26.0",
}
Any help would be appreciated.

Answer 1

In webpack4 the configuration should be loader: "babel-loader" but not use: "babel-loader"
rules: [
{
//tell webpack to use jsx-loader for all *.jsx files
test: /\.(jsx?)$/,
exclude: /node_modules/,
loader: "babel-loader"
},
]
Here is my working demo of webpack4
Versions I am using
"webpack": "^4.15.0",
"webpack-cli": "^3.0.8",
"webpack-dev-server":"^3.1.4",
"babel-core": "^6.26.3",
"babel-loader": "^7.1.5",
"babel-plugin-transform-class-properties": "^6.24.1",
"babel-plugin-transform-object-rest-spread": "^6.26.0",
"babel-polyfill": "^6.26.0", "babel-preset-env": "^1.7.0",
"babel-preset-react": "^6.24.1"
const path = require("path");
const HtmlWebpackPlugin = require("html-webpack-plugin");
const CompressionPlugin = require("compression-webpack-plugin");
const webpack = require('webpack');
module.exports = {
target: "web",
entry: [
"whatwg-fetch",
'webpack-dev-server/client?http://localhost:8090',
'webpack/hot/only-dev-server',
'babel-polyfill',
"./src/index.js"
],
output: {
path: path.resolve(__dirname, "build"),
filename: "bundle.js",
publicPath: "/"
//make sure port 8090 is used when launching webpack-dev-server
},
plugins: [new HtmlWebpackPlugin({
template: "index.html"
}),
new CompressionPlugin({
asset: "[path].gz[query]",
algorithm: "gzip",
test: /\.js$|\.jsx$|\.css$|\.html$/,
threshold: 10240,
minRatio: 0.8
}),
new webpack.HotModuleReplacementPlugin(),
// enable HMR globally
new webpack.NoEmitOnErrorsPlugin(),
new webpack.ProvidePlugin({
jQuery: 'jquery',
$: 'jquery',
jquery: 'jquery'
})
],
module: {
rules: [
{
//tell webpack to use jsx-loader for all *.jsx files
test: /\.(js|jsx)$/,
exclude: /node_modules/,
loader: "babel-loader"
},
{
test: /\.css$/,
loader: "style-loader!css-loader"
},
{
test: /\.(png|jpg|jpeg|gif|woff|woff2|svg)$/,
loader: 'url-loader?limit=100000'
},
{
test: /\.(eot|ttf)$/,
loader: "file-loader"
},
{
test: /\.html$/,
exclude: /node_modules/,
loader: 'html-loader'
},
{
test: /\.scss$/,
loaders: ["style-loader", "css-loader", "sass-loader"]
}
]
},
resolve: {
modules: [
path.resolve("./src"),
path.resolve("./node_modules")
],
extensions: [".js", ".jsx"]
},
devServer: {
watchOptions: {
// Needed for Windows Subsystem for Linux dev environment:
poll: true
},
contentBase: "/build"
},
devtool: "cheap-module-eval-source-map",
node: {
child_process : "empty",
fs: "empty"
}
};

Answer 2

Try clearing your node_modules cache and re-installing if you haven't yet:
rm -rf node_modules/
rm -rf ~/.npm
npm cache verify
npm install