Customizing Native Form Validation

baseline.js

var validateForm = function(submitEvent) {
  /* We'll fill this in incrementally. */
};

document.addEventListener('DOMContentLoaded', function() {
  var forms = document.querySelectorAll('form');

  for (var index = forms.length - 1; index >= 0; index--) {
    var form = forms[index];

    form.noValidate = true;
    form.addEventListener('submit', validateForm);
  }
});