Aurelia - bootstrap form validation feature

bootstrap-validation\bootstrap-form-validation-renderer.js

// For bootstrap 4 and I18N 


import { inject } from 'aurelia-framework'
import { RenderInstruction, ValidateResult } from 'aurelia-validation';
import {I18N} from "aurelia-i18n";

@inject(I18N)
export class BootstrapFormRenderer {

  public constructor (private i18n : I18N){ }

  public render(instruction: RenderInstruction) {
    for (let { result, elements } of instruction.unrender) {
      for (let element of elements) {
        this.remove(element, result);
      }
    }

    for (let { result, elements } of instruction.render) {
      for (let element of elements) {
        this.add(element, result);
      }
    }
  }

  public add(element: Element, result: ValidateResult) {
    if (result.valid) {
      if (!element.classList.contains('is-invalid')) {
        element.classList.add('is-valid');
      }
    } else {
      // add the has-error class to the enclosing form-group div
      element.classList.remove('is-valid');
      element.classList.add('is-invalid');

      // add help-block
      const message = document.createElement('div');
      message.className = 'help-block invalid-feedback';
      message.textContent = this.i18n.tr(result.message);
      message.id = `validation-message-${result.id}`;

      element.parentNode.insertBefore(message, element.nextSibling);
    }
  }

  public remove(element: Element, result: ValidateResult) {
    if (result.valid) {
      if (element.classList.contains('is-valid')) {
        element.classList.remove('is-valid');
      }
    } else {
      // remove help-block
      const message = element.parentElement.querySelector(`#validation-message-${result.id}`);
      if (message) {
        element.parentElement.removeChild(message);

        element.classList.remove('is-invalid');
      }
    }
  }
}

bootstrap-validation\index.js

import {BootstrapFormValidationRenderer} from './bootstrap-form-validation-renderer';

export function configure(config) {
  config.container.registerHandler(
    'bootstrap-form',
    container => container.get(BootstrapFormValidationRenderer));
}

I started to write a BS 4 version, then I found this one. Thank you!