//index.js

 require('./index.css')
 module.exports = function(){
  console.log(`I'm jack`)
  var a = 12
 }

//index.css

 .selected : {
   display: flex;
   transition: all .6s;
   user-select: none;
   background: linear-gradient(to bottom, white, black);
 }

 var extractTextPlugin = require('extract-text-webpack-plugin'),
  path = require('path')
 
 module.exports = {
  context : path.join(__dirname,'src'),
  entry:{
  main: './index.js',
  vender:['./jquery.js','./test.js']
  },
  module:{
  rules:[{
   test:/\.css$/,
   use: extractTextPlugin.extract({
   fallback:'style-loader',
   use:'css-loader'
   })
  }]
  },
  output:{
  path:path.join(__dirname, '/dist/js'),
  filename: 'bundle.[name].[hash].js',
  },
  plugins:[
  new extractTextPlugin('../css/bundle.[name].[hash].css')
  ]
 }

 var extractTextPlugin = require('extract-text-webpack-plugin'),
  path = require('path')
 
 module.exports = {
  ...
  ...
  output:{
  path:path.join(__dirname, '/dist/js'),
  filename: 'bundle.[name].[chunkhash].js',
  },
  plugins:[
  new extractTextPlugin('../css/bundle.[name].[chunkhash].css')
  ]
 }

 var extractTextPlugin = require('extract-text-webpack-plugin'),
  path = require('path')
 
 module.exports = {
  ...
  ...
  output:{
  path:path.join(__dirname, '/dist/js'),
  filename: 'bundle.[name].[chunkhash].js',
  },
  plugins:[
  new extractTextPlugin('../css/bundle.[name].[contenthash].css')
  ]
 }