JSFiddle - React, Tailwind, and code Playground

HTML

<form action="send.php" id="myform" method="post">
    <label>Your name:</label>
    <input type="text" name="username" placeholder="Type your name" id="username" class="required" />
    <label>Your email:</label>
    <input type="text" name="email" placeholder="Type your email address" id="email" class="required" />
    <label>Subject / Title:</label>
    <input type="text" name="subject" placeholder="Title / Subject" class="required" />
    <label>Write us something:</label>
    <textarea col="99" placeholder="Describe as detailed as possible, what you want us to do, for you. Send what you want and we will reply to you, as soon as possible!" id="message"></textarea>
    <input onclick="return validateForm();" type="submit" name="submit" value="Enviar" id="submit" />
</form>
<div class="alert alert-warning hidden" id="warning">An error has occured! Please fill your email and message!</div>
<div class="alert alert-success hidden" id="success">Message sent! We will reply to you, as soon as possible!</div>

JavaScript

function validateForm() {
    if ($("#message").val() == "") {
        $("#warning").removeClass("hidden");
        $("#warning").addClass("show");
        $('#warning').delay(5000).fadeOut(500);
        return false;
    } else {
        $("#sucess").removeClass("hidden");
        $("#success").addClass("show");
        $('#sucess').delay(5000).fadeOut(500);
        return true;
    }
}