webpack.config.js

const webpack = require("webpack"),
    path = require("path"),
    CopyWebpackPlugin = require("copy-webpack-plugin"),
    HtmlWebpackPlugin = require("html-webpack-plugin"),
    WriteFilePlugin = require("write-file-webpack-plugin");

if (process.env.NODE_ENV == null) {
    process.env.NODE_ENV = 'development';
}
const ENV = process.env.ENV = process.env.NODE_ENV;

const plugins = [
    new webpack.DefinePlugin({
        'process.env': {
            'ENV': JSON.stringify(ENV)
        }
    }),
    new CopyWebpackPlugin({
        patterns: [{
            from: "manifest.json"
        },{
            from: "src/images",
            to: "images"
        },{
            from: "src/css/*.css",
            to({ context, absoluteFilename }) {
                return "contentscript/[name][ext]";
            }
        }]
    }),
    new WriteFilePlugin()
];

const fileExtensions = ["jpg", "jpeg", "png", "gif", "eot", "otf", "svg", "ttf", "woff", "woff2"];
const moduleRules = [
    {
        test: /\.css$/,
        use: ["style-loader", "css-loader"],
        exclude: /node_modules/
    },
    {
        test: new RegExp('.(' + fileExtensions.join('|') + ')$'),
        use: "file-loader?name=[name].[ext]",
        exclude: /node_modules/
    },
    {
        test: /\.html$/,
        use: {
            loader: "html-loader",
            options: {
                sources: false
            }
        },
        exclude: /node_modules/
    }
];

const config = {
    target: 'web',
    devtool: "cheap-module-source-map",
    mode: process.env.NODE_ENV || "development",
    entry: {
        'contentscript/index': path.join(__dirname, "src", "contentscript", "index.js"),
        'background': path.join(__dirname, "background.js"),
    },
    output: {
        path: path.join(__dirname, "dist"),
        filename: "[name].bundle.js",
        clean: true
    },
    module: {
        rules: moduleRules
    },
    plugins: plugins
};

if (ENV === "development") {
    config.devtool = 'cheap-module-source-map';
}

module.exports = config;