Element: focusin event

<form id="form">
  <input type="text" placeholder="text input">
  <input type="password" placeholder="password">
</form>

const form = document.getElementById('form');

form.addEventListener('focusin', (event) => {
  event.target.style.background = 'pink';
});

form.addEventListener('focusout', (event) => {
  event.target.style.background = '';
});