validation modifer - running validations

controllers.application\.js

import Controller from '@ember/controller';
import { action } from '@ember/object';
import { isBlank } from '@ember/utils';

export default class ApplicationController extends Controller {

  @action
  handleValidated({ target: { validationMessage, name } }) {
    console.log('did-validate event caught by form');
    console.table([{
      "input name": name,
      value: arguments[0].target.value,
      isValid: isBlank(validationMessage),
      "validation error message": validationMessage         
    }]);
  }
  
  @action
  validatePresence({ value }) {
    if(isBlank(value)) {
      return "input cannot be empty";
    }
  }

  @action
  validateEmail({ value }) {
  	const re = /^(([^<>()[\]\\.,;:\s@"]+(\.[^<>()[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
    if(!re.test(String(value))) {
      return "email is not valid";
    }
  }
}

modifiers.validation\.js

import { modifier } from 'ember-modifier';
import { assert } from '@ember/debug';

// transforms a coma separated string of events into an array
// 'blur ,input,, change' becomes ['blur', 'input', 'change'] 
function parseEventsList(string) {
  return string
    .split(',')
    .map(i => i.trim())
    .filter(Boolean);
}

async function runValidators(validators, input) {
  // returns a single Promise that resolves to an array of the results
  // of the input validators (validation functions)
  let errors = await Promise.all(validators.map(validator => validator(input)));
  return errors.filter(Boolean);
}

function addEventListeners(input, eventsToValidateOn, validators) {
  async function runValidation() {
    // destructure the first error message of the array 
    // or set error to ''
    let foo = await runValidators(validators, input);
		let [error = ''] = foo;
    input.setCustomValidity(error);
    input.dispatchEvent(new CustomEvent('did-validate', { bubbles: true }));
  }

  eventsToValidateOn.forEach(eventName => {
    input.addEventListener(eventName, runValidation);
  });

  return { runValidation };
}

function validation(
  input,
  validators,
  { on: eventNames = 'change,input,blur' }
) {
    let eventsToValidateOn = parseEventsList(eventNames);
    
    let { runValidation } = addEventListeners(
      input,
      eventsToValidateOn,
      validators
    );

    function cleanupEventListeners() {
      eventsToValidateOn.forEach(eventName => {
        input.removeEventListener(eventName, runValidation);
      });
    }

    // When the modifier is destroyed, 
    // clean up the changes that the modifier made in the first place
    return cleanupEventListeners;
}

export default modifier(validation);

styles.app\.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

form {
  display: flex;
  flex-direction: column;
}

label {
  margin-bottom: 4px;
  margin-top: 24px;
}

input {
  height: 30px;
}

.error {
  color: red;
}

h2 {
  border: dotted red;
  padding: 8px;
  text-align: center;
}

templates.application\.hbs

<h1>Ember Form Validation API Demo - Running validations</h1>

<h2> open your console and try to fill in the form </h2>

<form 
	{{on 'did-validate' this.handleValidated}}
  novalidate
  >
  <label for="firstname-input">
  	Enter your first name
  </label>
	<input 
  	id="firstname-input"
  	name="firstname"
    autocomplete="off"
    {{validation this.validatePresence}}/>
    
  <span class="error">{{this.validations.firstname.message}}</span>
  
  <label for="email-input">
  	Enter your email address
  </label>
  <input 
  	id="email-input"
  	name="email"
    autocomplete="off"
    {{validation this.validatePresence this.validateEmail}}/>
    
   <span class="error">{{this.validations.email.message}}</span>
</form>

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0",
    "ember-modifier": "3.0.0"
  }
}