Demonstration of CPS vs EE

hybrid.js

'use strict'

// Dependencies
const EventEmitter = require('events').EventEmitter
const path = require('path')

// Definition
function findFiles (files, extension, cb = null) {
  const emitter = new EventEmitter()
  const errorMessage = 'no files supplied';

  if (files.length === 0) {
    if (cb) {
      cb(errorMessage)
    }
    emitter.emit('error', errorMessage)
  }

  if (cb) {
    // cps
    let result = []
    for (let i = 0; i < files.length; ++i) {
      if (path.extname(files[i]) === extension) {
        result.push(files[i])
      }
    }
    cb(null, result)
  } else {
    // event emitter style
    process.nextTick(() => {
      files.forEach(file => {
        if (path.extname(file) === extension) {
          emitter.emit('match', file)
        }
      })
    })

    return emitter
  }
}

// Implementation with a callback
findFiles(process.argv.slice(2), '.js', (err, result) => {
  if (err) return console.error(err)
  console.log(`All in one: ${result}`)
})

// Implementation with an event emitter
findFiles(process.argv.slice(2), '.js')
  .on('match', file => console.log(file + ' is a match'))
  .on('error', err => console.log('Error emitted: ' + err.message))