Tampermonkey script to copy the selection in f-puzzles.com

fpuzzles-copyselection.js

// ==UserScript==
// @name         Copy selection
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Copy the value of selected cells
// @author       Stephen Checkoway
// @match        https://*.f-puzzles.com/*
// @match        https://f-puzzles.com/*
// @icon         https://www.google.com/s2/favicons?domain=f-puzzles.com
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    const doShim = function() {
        const prevOnKeyDown = document.onkeydown;
        document.onkeydown = function(event) {
            if (event.key != 'c' || !(event.ctrlKey || event.metaKey)) {
                prevOnKeyDown(event);
                return;
            }

            let output = "";
            for (let idx = 0; idx < window.selection.length; ++idx) {
                output += window.selection[idx].value;
            }

            navigator.clipboard.writeText(output);
            event.preventDefault();
        }
    }

    if (window.grid) {
        doShim();
    } else {
        document.addEventListener('DOMContentLoaded', (event) => {
            doShim();
        });
    }
})();