JSFiddle - React, Tailwind, and code Playground

HTML

<form name="loginForm" method="post" action="">
    <input type="text" name="username" id="username">
    <input type="password" name="password" id="password">
    <input type="submit" name="submit" id="submit">
</form>

JavaScript

$('form').submit(function(e) {
    loginValidation();
    e.preventDefault();
});

function loginValidation()
{
                var username = $('#username').val();
                var password = $('#password').val();
                if (username == "" || password == "" )
                {
                    alert("Invalid entry...!!!");
                    return false;
                }
}