JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <form action="activate_account.php" method="post" id="accountActivation">
        <tr>
            <td align="right">
                <label for="new_password">Password (6-12 chars):</label>
            </td>
            <td>
                <input type="password" name="new_password" id="new_password" />
            </td>
        </tr>
        <tr>
            <td align="right">
                <label for="new_password2">Again:</label>
            </td>
            <td>
                <input type="password" name="new_password2" id="new_password2" />
            </td>
        </tr>
        <tr>
            <td>
                <td>
                    <div class="registrationFormAlert" id="divCheckPasswordMatch">Passwords missmatch</div>
                </td>
                <td>
                    <div id="submit">
                        <button id="buttonActivate" type="submit" disabled="disabled">Activate Account</button>
                    </div>
                </td>
        </tr>
</table>

JavaScript

$(document).ready(function() {
    $(".registrationFormAlert").hide();
    function checkPasswordMatch() {
        var password = $("#new_password").val();
        var confirmPassword = $("#new_password2").val();


        if (password != confirmPassword) {
            $("#new_password").css("background", "red");
            $("#new_password2").css("background", "red");
            $("#buttonActivate").prop("disabled", true);
            $(".registrationFormAlert").show();
            return false;
        } else {
            $("#new_password").css("background", "green");
            $("#new_password2").css("background", "green");
            $("#buttonActivate").prop("disabled", false);
            $(".registrationFormAlert").hide();
            return true;
        }

    }
    $("input").keydown(function() {
        var password = $("#new_password").val();
        var confirmPassword = $("#new_password2").val();
        if (password.length >= 6 && confirmPassword.length >= 6) {
            checkPasswordMatch();
        }
    });
});