medium-moment-every-example.js

const characters = [
  { name: 'Professor', appearAt: '10/05/2017 10:10:10'}, 
  { name: 'Nairobi', appearAt: '10/05/2017 12:10:10' },
  { name: 'Tókyo', appearAt: '10/06/2017 07:10:10' },
  { name: 'Rio', appearAt: '10/06/2017 09:10:10' },
  { name: 'Denver', appearAt: '10/07/2018 11:10:10' }, 
  { name: 'Berlim', appearAt: '10/07/2018 17:10:10' },
  { name: 'Helsinque', appearAt: '15/04/2017 12:10:10' },
  { name: 'Moscou', appearAt: '15/04/2017 12:10:10' }, 
  { name: 'Raquel Murillo', appearAt: '10/09/2020 29:10:10' }
]

const dateFormat = 'DD/MM/YYYY HH:mm:ss'

const allDateIsValid = () => {
  return characters.every(character => {
    return moment(character.appearAt, dateFormat, true).isValid()
  })
}

// false