JSFiddle - React, Tailwind, and code Playground

HTML

<div ng-app>
    
    <form action="#" novalidate name="register" ng-submit="(submitted=true) && register.$invalid && $event.preventDefault()" ng-class="{true:'submitted'}[submitted]">
        <input type="text" ng-model="user.username" required> 
        <input type="email" ng-model="user.email">
        <input type="submit">
    </form>
</div>

SCSS

.submitted{
    .ng-invalid{
        border: 15px solid red;
    }
}