The checkValidity() method of the HTMLFieldSetElement interface checks if the element is valid, but always returns true because <fieldset> elements are never candidates for constraint validation.
Note: The :valid and :invalid CSS pseudo-classes are applied to <fieldset> elements based on the validity of its descendant form controls, not the fieldset itself.
checkValidity()None.
A boolean value, true.
In the following example, calling checkValidity() returns true.
const element = document.getElementById("myFieldSet");
console.log(element.checkValidity());