User script to add links to stackprinter.com for pretty printing SO questions and answers

stackprinter.user.js

// ==UserScript==
// @name           Pretty print stackoverflow questions and answers
// @namespace      gist.github.com/StefRe
// @description    Add links to stackprinter for SO questions and answers
// @include        https://stackoverflow.com/questions/*
// @include        https://serverfault.com/questions/*
// @include        https://superuser.com/questions/*
// @include        https://stackapps.com/questions/*
// @include        https://askubuntu.com/questions/*
// @include        https://mathoverflow.net/questions/*
// @include        https://*.stackexchange.com/questions/*
// @include        https://*.stackoverflow.com/questions/*
// @include        https://*.serverfault.com/questions/*
// @include        https://*.superuser.com/questions/*
// @include        https://*.stackapps.com/questions/*
// @include        https://*.askubuntu.com/questions/*
// @include        https://*.mathoverflow.net/questions/*
// @version        1.0
// @grant          none
// ==/UserScript==
function openUrl() {
    const url = this.dataset.url;
    if (!window.open(url)) {
        location.href = url;
    }
}

function printLink(url) {
    const printA = document.createElement('a');
    printA.innerHTML = '🖨️';
    printA.style.cursor = 'pointer';
    printA.onclick = openUrl;
    printA.setAttribute('data-url', url);
    printA.style.fontSize = 'x-large';
    const printDiv = document.createElement('div');
    printDiv.style.textAlign = 'center'
    printDiv.appendChild(printA);
    return printDiv;
}

const re = new RegExp('^https://(.*)\.(?:com|net)/questions/([0-9]*)/');
const group = re.exec(window.location.href);
const spurl = 'http://www.stackprinter.com/export?format=HTML&service=' + group[1] + '&question=' + group[2];

const question = document.getElementsByClassName('question')[0].getElementsByClassName('js-vote-down-btn')[0];
question.parentNode.insertBefore(printLink(spurl), question.nextSibling);

for (let answer of document.getElementsByClassName('answer')) {
    let vdbtn = answer.getElementsByClassName('js-vote-down-btn')[0];
    vdbtn.parentNode.insertBefore(printLink(spurl + '&answer=' + answer.getAttribute('data-answerid')), vdbtn.nextSibling);
}