JavaScript popup window message passing example

index.html

<script>
const windowName = 'MyApp'
const options = 'location=0,status=0,width=800,height=400'
const path = 'http://localhost:9000/auth'
const child = window.open(path, windowName, options)

let myValue = ''
let messagePosted = false

window.addEventListener('message', event => {
  if (event.data.complete) {
    myValue = event.data.myValue
    child.close()
  }
})

const interval = setInterval(() => {
  if (!messagePosted) {
    child.postMessage({domain: window.location.host}, '*')
    messagePosted = true
  }

  if (child.closed) {
    clearInterval(interval);
    callback(null, {username})
   }
}, 100)
</script>

popup.html

<script>
const form = document.querySelector('#form')
const input = document.querySelector('#input')

window.addEventListener('message', event => {
  if (event.data.domain) {
    domain.innerHTML = event.data.domain
  }
})

form.addEventListener('submit', event => {
  event.preventDefault()
  const data = {complete: true, myValue: input.value}
  window.opener.postMessage(data, '*')
})
</script>