How to set the view to the wrong fields after submit?

Question

JavaScript

Hello. if you set the style for the :invalid selector, then it is applied immediately, i.e. when the fields are still empty. How can I make, roughly speaking, inputs with incorrect data be in a red border after submit?

Answer 1

Ну вот примерно так можно сделать https://jsfiddle.net/ov4non3j/

Answer 2

<form ... onsubmit="validator()">
</form>

Answer 3

Well, add a class to these inputs, and remove them when they become valid. what is the problem?
Or are we able to download all sorts of bootstraps, but does everything else baffle?