JSFiddle - React, Tailwind, and code Playground

HTML

<form action="login.php" method="post">
    <label>Login Name:</label>
    <input type="text" name="email" id="log" />
    <label>Password:</label>
    <input type="password" name="password" id="pwd" />
    <input type="submit" name="submit" value="Login" />
</form>

CSS

.text-label {
    color: #cdcdcd;
    font-weight: bold;
}

JavaScript

//  Bind the event handler to the "submit" JavaScript event
$('form').submit(function () {

    // Get the Login Name value and trim it
    var name = $.trim($('#log').val());

    // Check if empty of not
    if (name === '') {
        alert('Text-field is empty.');
        return false;
    }
});