Async events handling strategies

gistfile1.js

// host library code
program()
  .initStuff()
  .then(function() {
    dispatcher.emit('beforeRenderPost')
  })
  .then(function() {
    dispatcher.emit('afterRenderPost')
  })
  .then(function() {
    dispatcher.emit('beforeWritePost')
  })
  .then(function() {
    dispatcher.emit('afterWritePost')
  })
  .catch(errorHandler)

// now the user's code can simply be the following and the host logic
// will wait until their async function is finished before continuing
dispatcher.on('beforeRenderPost', doSomethingAsyncToPost)

would basically need to check against the expected Function.length to define if you should wait for callback call or not

I originally considered this. Like, if the callback function's .length property is one greater than the emitter's arguments.length property, assume async, but that won't work 100% of the time. Sometimes a callback will make use of the arguments object for ...rest parameter type situations, so it gets a bit hairy.