How do you validate a form natively?

<input type="email" required minlength="5" maxlength="80">
<input type="number" min="1" max="10" step="1">
<input pattern="[0-9]{3}-[0-9]{4}" title="Format: 123-4567">

input.checkValidity();     // true/false, fires an "invalid" event if false
input.reportValidity();    // same, and shows the browser's bubble
input.validationMessage;   // the localised message
input.validity.valueMissing;   // which constraint failed
input.validity.typeMismatch;
input.validity.tooShort;
input.validity.patternMismatch;

confirm.addEventListener("input", () => {
  confirm.setCustomValidity(
    confirm.value === password.value ? "" : "Passwords do not match"
  );
});

<form novalidate>

form.addEventListener("submit", (e) => {
  if (!form.checkValidity()) {
    e.preventDefault();
    for (const el of form.elements) showError(el, el.validationMessage);
  }
});