A very, very rough draft of a custom field to perform validations on its input. (has not been tested)

field.js

/**
 * A higher-order microstate that takes a validation function, and returns
 * a field class that validates the input of that field based on inputs.
 */
export function Field(validationFn) {
  return class Field extends String {
    get validation() {
      return validationFn(valueOf(this));
    }   
    get hasErrors() {
      return this.validation.messages.length > 0;
    }
  }
}

user-form.js

import Field from './field';

import { notEmpty } from './my-validation-lib';

/**
 * An example microstate composing two fields:
 *
 */
export class UserForm {
  firstName = Field(notEmpty);
  lastName = Field(notEmpty);
}