text: const element = element => document.querySelector(element)
  const verify = (name, email, tel, message) => name && email && tel && message ? true : false
  
  // arrow function de validação de email a partir de uma definição em regex retornano true ou false
  const validateEmail = email => {
      let regex = /\S+@\S+\.\S+/
      return regex.test(email)
  }
  
  const fieldName = element('#name')
  const fieldEmail = element('#email')
  const fieldFone = element('#tel')
  const areaMessage = element('#message')
  const btn = element("section#contacts form button")
  
  let name = false
  let email = false
  let tel = false
  let message = false
  
  fieldName.addEventListener('keyup', () => {
      fieldName.value.length < 1 ? name = false : name = true
  
      if(verify(name, email, tel, message)){
          btn.removeAttribute('disabled')
          btn.classList.remove('btn-disable')
          btn.classList.add('btn-enable')
      }
      else{
          btn.setAttribute('disabled', '')
          btn.classList.remove('btn-enable')
          btn.classList.add('btn-disable')
      }
  })
  
  fieldEmail.addEventListener('keyup', () => {
      validateEmail(fieldEmail.value) ? email = true : email = false
  
      if(verify(name, email, tel, message)){
          btn.removeAttribute('disabled')
          btn.classList.remove('btn-disable')
          btn.classList.add('btn-enable')
      }
      else{
          btn.setAttribute('disabled', '')
          btn.classList.remove('btn-enable')
          btn.classList.add('btn-disable')
      }
  })
  
  fieldFone.addEventListener('keyup', () => {
      fieldFone.value.length < 1 ? tel = false : tel = true
      
      if(verify(name, email, tel, message)){
          btn.removeAttribute('disabled')
          btn.classList.remove('btn-disable')
          btn.classList.add('btn-enable')
      }
      else{
          btn.setAttribute('disabled', '')
          btn.classList.remove('btn-enable')
          btn.classList.add('btn-disable')
      }
  })
  
  areaMessage.addEventListener('keyup', () => {
      areaMessage.value.length < 1 ? message = false : message = true
      
      if(verify(name, email, tel, message)){
          btn.removeAttribute('disabled')
          btn.classList.remove('btn-disable')
          btn.classList.add('btn-enable')
      }
      else{
          btn.setAttribute('disabled', '')
          btn.classList.remove('btn-enable')
          btn.classList.add('btn-disable')
      }
  })
  
  element('footer p span.year').innerHTML = new Date().getFullYear()