I am a monster.

evil.js

var Emitter = require('events').EventEmitter
var evil = new Emitter

evil.on('foo', function (get) {
  console.log('privateThing is', get('privateThing'))
})

function foo () {
  var privateThing = 'secret'
  evil.emit('foo', function (prop) {
    return eval(prop)
  })
}

foo()