Error: Can't resolve 'fs' in （webpack 2配置CSS loadeers）

前言，在之前有配置过webpack 2 中css loaders，但是怎么也不正确

报错：

ERROR in ./~/convert-source-map/index.js
Module not found: Error: Can't resolve 'fs' in '/Users/ceshi/Desktop/webpack/node_modules/convert-source-map'
 @ ./~/convert-source-map/index.js 2:9-22
 @ ./~/css-loader/lib/css-base.js
 @ ./~/css-loader!./app/style.css
 @ ./app/style.css
 @ ./app/main.js

解决方法，修改webpack的配置文件，增加一句代码

 node: {
        fs: 'empty'
    },