Press ctrl+value with nothing selected to select all markings with that value

fpuzzles-selectval.js

// ==UserScript==
// @name         Fpuzzles-SelectValue
// @namespace    http://tampermonkey.net/
// @version      1.2
// @description  Press ctrl+value with nothing selected to select all markings with that value
// @author       Rangsk
// @match        https://*.f-puzzles.com/*
// @match        https://f-puzzles.com/*
// @icon         data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==
// @grant        none
// @run-at       document-end
// ==/UserScript==

(function() {
    const doShim = function() {
        'use strict';

        const prevOnKeyDown = document.onkeydown;
        document.onkeydown = function(event) {
            if ((event.key < '1' || event.key > '9') ||
                popup ||
                disableInputs ||
                testPaused() ||
                window.selection && window.selection.length !== 0 ||
                !event.ctrlKey ||
                event.altKey ||
                event.metaKey) {
                prevOnKeyDown(event);
            } else {
                window.selection = [];
                const val = event.key - '0';
                const size = window.size;
                for (let i = 0; i < size; i++) {
                    for (let j = 0; j < size; j++) {
                        const cell = window.grid[i][j];
                        if (cell.value === val || cell.centerPencilMarks.includes(val) || cell.cornerPencilMarks.includes(val)) {
                            selection.push(cell);
                        }
                    }
                }
                event.preventDefault();
            }
        }
    }

    let intervalId = setInterval(() => {
        if (!document.onkeydown) {
            return;
        }

        clearInterval(intervalId);
        doShim();
    }, 16);
})();