review_countdown.user.js

// ==UserScript==
// @name        Review Countdown
// @namespace   Violentmonkey Scripts
// @match       https://jpdb.io/review
// @grant       none
// @version     2.0
// @author      hmry
// @description 5/7/2022, 10:07:03 PM
// ==/UserScript==

let SECONDS = 6;
let AUTOREVEAL = false;

// Code starts here

const kindTextElem = document.querySelector('.kind');
if (kindTextElem) {
    kindTextElem.insertAdjacentHTML('beforebegin', `
    <div class="countdown" style="font-size: 200%; text-align: center;">${SECONDS}</div>
    `);

    const countdown = document.querySelector('.countdown');

    const interval = setInterval(() => {
        SECONDS -= 1;

        if (!countdown.classList.contains('countdown')) {
            // Our element was removed - the user answered?
            clearInterval(interval);
        } else if (SECONDS <= 0) {
            clearInterval(interval);
            countdown.innerText = `!! ${SECONDS} !!`;
            countdown.style.color = 'red';
            if (AUTOREVEAL)
                document.querySelector('form[action="/review#a"]').submit();
        } else {
            countdown.innerText = `${SECONDS}`;
        }
    }, 1000)
}