index.js

var myModule = require('./my-module.js')

myModule.yo()
// prints 'yo'

myModule.myDefault()
// prints 'hi'

myModule.whisper()
// error `whisper` is undefined because we haven't exported it

my-module.js

function yo () {
  console.log('yo')
}

function hi () {
  console.log('hi')
}

function whispher () {
  console.log('pssst')
}

module.exports = {
  yo: yo,
  myDefault: hi
}