User script to control Duolingo with Keyboard

duolingo-keyboard-control.js

// ==UserScript==
// @name         Duolingo Keyboard Control
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Add full keyboard control to Duolingo (to tiles). Shortcuts: 0-9, shift + 0-9, and "\"
// @author       Matthew Scholefield
// @match        https://www.duolingo.com/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    // Dynamic names of parent elements of the button containers.
    const buttonParent1 = '._1PGxI', buttonParent2 = '._30i_q', buttonParent3 = '._30i_q', sentParent1 = '._6HogY', sentParent2 = '_2T9b4';

    const charToKey = {
        '!': 1,
        '@': 2,
        '#': 3,
        '$': 4,
        '%': 5,
        '^': 6,
        '&': 7,
        '*': 8,
        '(': 9,
        ')': 0
    };

    const getNum = d => d == 0 ? 9 : d - 1;

    document.addEventListener('keypress', ({ ctrlKey, shiftKey, key }) => {
        var parent = document.querySelector(buttonParent1) || document.querySelector(buttonParent2);
        var sentParent = document.querySelector(sentParent1) || document.querySelector(sentParent2);
        var d = parseInt(key);
        if (!isNaN(d)) {
            parent.childNodes[getNum(d)].click();
        }
        if (key === '\\') {
            sentParent.childNodes[sentParent.childNodes.length - 1].click();
        }
        d = charToKey[key];
        if (d !== undefined) {
            hoverParent.childNodes[getNum(d)].click();
        }
    })
})();