JSFiddle - React, Tailwind, and code Playground

HTML

<form action="" id="form_cadastra">
    <input type="email" />
    <input type="email" />
    <input type="email" />
    <input type="submit" value="Send" />
</form>

CSS

.vazio {
    border-color:red;
}

JavaScript

$(function () {
    $("#form_cadastra").submit(function () {
        var vazios = $("input[type=email]").filter(function() {
            return !this.value;
        }).get();

        if (vazios.length) {
            $(vazios).addClass('vazio');
            alert("Todos os campos devem ser preenchidos.");
            return false;
        } else {
            alert("Eureka");
        }
    });
});