CoffeeScript with Tree Shaking

foo.coffee

export foo = 'foo'
export unused = -> foo

index.coffee

import {foo} from './foo.coffee'
console.log foo

package.json

{
  "dependencies": {
    "coffee-loader": "^0.7.3",
    "coffee-script": "^1.12.6",
    "webpack": "^2.5.1"
  }
}

webpack.config.json

module.exports = {
  entry: './index.coffee',
  output: {
    filename: 'bundle.js'
  },
  module: {
    rules: [
      {
        test: /\.coffee$/,
        use: [ 'coffee-loader' ]
      }
    ]
  }
}