class prefixer using postcss-loader for webpack

post-css-prefix-webpack-config.js

import classPrfx from 'postcss-class-prefix';
import precss from 'precss';    // for scss support

module: {
  loaders: [
    {
        test: /\.scss$/,
        loaders: [
            'style',
            'css',
            'postcss'
            'sass'
        ]
    },    
    {
      test: /\.css$/,
      loader: 'style-loader!css-loader?!postcss-loader'
      // loader: 'css?camelCase&modules&importLoaders=1&localIdentName=[name]___[local]___[hash:base64:5]',  // modules support
    },
  ]  
},
postcss() {
  return [ precss, classPrfx('my-prefix-', { ignore: [/some-class-/] }) ];
}

prefix-class-task.js

var fs        = require('fs');
var postcss   = require('postcss');
var classPrfx = require('postcss-class-prefix');

var css = fs.readFileSync('/index.css', 'utf8').toString();
var out = postcss()
          .use(classPrfx('my-prefix-'))
          .process(css);

fs.writeFileSync('/prefixed.css', out);