index.js

var path = require('path')
var babel = require('babel-loader')
var css = require('css-loader')

module.exports = function (source, map) {
  switch (path.extname(this.resourcePath)) {
    case '.js': return babel.apply(this, arguments)
    case '.css': return css.apply(this, arguments)
    default: return source
  }
}

metaloader-test.js

var fs = require('fs')
var path = require('path')
var webpack = require('webpack')
var meta = require('../')

var entriesDirectory = path.join(__dirname, 'entries')
var buildsDirectory = path.join(__dirname, 'builds')
var entries = {}

fs.readdirSync(entriesDirectory).forEach(function (entry) {
  var entryName = path.basename(entry, path.extname(entry))
  entries[entryName] = './' + path.relative(__dirname, path.join(entriesDirectory, entry))
})

webpack({
  debug: true,
  context: __dirname,
  entry: entries,
  output: { path: buildsDirectory, filename: '[name].js' },
  module: { loaders: [{ loader: 'meta-loader' }] }
}, function () {
  console.log('complete')
})