1 Feld

document.getElementsByClassName('step__footer__continue-btn btn')[0].addEventListener(
   'click',
   function(event) {
      value0 = document.getElementById('checkout_shipping_address_address1').value;

      if (!containsNumber(value0)) {
         alert('Bitte Hausnummer angeben!');
         event.preventDefault();
      }
   }
);

function containsNumber(str) {
  return /\d/.test(str);
}