EcmaScript | ES6 promises.js

const promise = (duration = 0) => {
    return new Promise((resolve, reject) => {
        setTimeout(resolve, duration)
    })
}

promise(1000)
  .then(() => {
    console.log('1 sec')
    return promise(500)
  })
  .then(() => {
    console.log('1.5 sec')
    return promise(500)
  })
  .then(() => {
    console.log('2 sec')
    return promise(500)
  })
  .then(() => {
    console.log('2.5 sec')
  })