Gravity Forms: Perform an action while the form is submitting

gravity-forms.js

/**
 * Hook into the Gravity Forms submission process to show a loading state
 */

const wrapper = document.querySelector(
  '.gform_wrapper'
);
const gfSubmitting = `gf_submitting_${
  wrapper.querySelector('form').dataset.formid
}`;
let formSubmitting = false; // Private variable to hold the state

// Create computed properties for the "gf_submitting_{id}" property
Object.defineProperty(window, gfSubmitting, {
  get() {
    return formSubmitting;
  },
  set(newValue) {
    if (formSubmitting !== newValue) {
      formSubmitting = newValue;
      // Do something when the state changes
      // Here, we're dialing down opacity while the AJAX spinner is spinning 
      wrapper.querySelector('.gform-body').style.opacity = newValue ? 0.3 : 1;
    }
  },
});