webpack.config.js

//webpack.config.js add code like that

const HtmlWebPackPlugin = require("html-webpack-plugin");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
var server_port = process.env.YOUR_PORT || process.env.PORT || 5000;
var server_host = process.env.YOUR_HOST || "0.0.0.0";

module.exports = {
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: {
          loader: "babel-loader"
        }
      },
      {
        test: /\.css$/,
        use: [MiniCssExtractPlugin.loader, "css-loader"]
      }
    ]
  },
  devServer: {
    disableHostCheck: true,
    contentBase: "./ dist",
    compress: true,
    inline: true,
    port: server_port,
    host: server_host

  },
  plugins: [
    new HtmlWebPackPlugin({
      template: "./src/index.html",
      filename: "index.html"
    }),
    new MiniCssExtractPlugin({
      filename: "[name].css",
      chunkFilename: "[id].css"
    })
  ]
};