How to specify Buefy field type more easily when doing a form validation

vee-validate-buefy-field-type.ts

/**
 * Returns an object with definition of <b-field :type> for Buefy.
 *
 * Instead of setting the field type like this:
 *
 *    <b-field :type="{ 'is-danger': errors.has('field_name') }"></b-field>
 *
 * You can now use it like this:
 *
 *    get fieldTypes() {
 *      return getFormFieldTypeOnError(Object.keys(this.formData), this.$validator.errors);
 *    }
 *
 *    <b-field :type="fieldTypes.field_name"></b-field>
 */
export function getFormFieldTypeOnError(formKeys: string[], errorBag: ErrorBag, errorType = 'is-danger') {
  const initialTypes = {};
  return formKeys.reduce((fieldTypes: object, field: string) => {
    const fieldTypeDef = {[errorType]: errorBag.has(field)};
    return {
      ...fieldTypes, [field]: fieldTypeDef,
    };
  }, initialTypes);
}