<form id="form">
  
  <div>
    必須
    <input type="text" required/>
  </div>
  
  <div>
    email + 必須
    <input type="email" required/>
  </div>
  
  <div>
    全角カタカナ + 必須
    <input type="text" pattern="[\u30A1-\u30FF]*" required/>
  </div>
  
  <button type="submit">送信</button>
</form>
input,
select {
  &:valid {
    border: 1px solid green;
  }
  &:invalid {
    border: 1px solid red;
  }
}

// 案件上デフォルトのstyleで使われることがほぼないのでstyleは適当
[type='radio'],
[type='checkbox'] {
  &:valid {
    box-shadow: green 0px 0px 3px 1px;
  }
  &:invalid {
    box-shadow: red 0px 0px 3px 1px;
  }
}
View Compiled 
const $form = document.getElementById('form');

// 親要素(form)にイベントをつけると子要素のイベントが拾える
$form.addEventListener('change', update);
$form.addEventListener('input', update);

function update(e) {
  let type = e.target.type;
  let validity = e.target.validity;
  console.log(type, validity);
}

External CSS

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External JavaScript

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