webpack.dev.config.js

const webpack = require('webpack');
const path = require('path');
const ExtractTextPlugin = require('extract-text-webpack-plugin');
const WriteFilePlugin = require('write-file-webpack-plugin');

const merge = require('webpack-merge');
const baseConfig = require('./webpack.base.config.js');

const cssLoader = {
    loader: 'css-loader',
    options: {
        sourceMap: true,
    },
};

const resolveUrlLoader = {
    loader: 'resolve-url-loader',
    options: {
        sourceMap: true,
        fail: true,
    },
};

const sassLoader = {
    loader: 'sass-loader',
    options: {
        outputStyle: 'expanded',
        sourceMap: true,
        sourceMapContents: true,
    },
};

const scssLoader = [cssLoader, resolveUrlLoader, sassLoader];

module.exports = merge(baseConfig, {
    entry: [
        'react-hot-loader/patch',
        './src/index.js'
    ],
    output: {
        path: path.join(__dirname, 'dist'),
        filename: '[name].[chunkhash].js',
        publicPath: "/"
    },
    module: {
        rules: [
            {
                test: /\.css$/,
                use: ExtractTextPlugin.extract({
                        use: cssLoader,
                    }
                )
            },
            {
                test: /\.scss$/,
                use: ExtractTextPlugin.extract({
                        use: scssLoader,
                        publicPath: "/"
                    }
                ),
            },

        ]
    },
    devtool: 'eval-source-map',
    plugins: [
        new WriteFilePlugin(),
        new webpack.DefinePlugin({
            'process.env.NODE_ENV': JSON.stringify('development')
        }),
    ]
});