Confirmation for following external links

external-links.js

const baseUrl = window.location.origin;
const absoluteUrlRegex = new RegExp('^(?:[a-z]+:)?//', 'i');

const isAbsoluteUrl = (url) => absoluteUrlRegex.test(url);
const isLocalUrl = (url) => url.startsWith(baseUrl) || !isAbsoluteUrl(url);

// https://gist.github.com/ -> github.com
const getDomain = (url) => {
    const urlInstance = new URL(url);
    const dividedUrl = urlInstance.hostname.split('.');
    const urlDomainsCount = dividedUrl.length;
    return urlDomainsCount === 2
        ? urlInstance.hostname
        : `${dividedUrl[urlDomainsCount - 2]}.${dividedUrl[urlDomainsCount - 1]}`;
};

const whitelist = [
    'twitter.com',
    'github.com',
    'stackoverflow.com',
    'facebook.com',
    'instagram.com',
];

const isWhitelistedUrl = (url) => {
    const domain = getDomain(url);
    return domain === window.location.hostname || whitelist.includes(domain);
};

// bind listener
const confirmExternalLinks = (confirmationFn) => {
    document.addEventListener('click', async (e) => {
        const linkElement = e.target.closest('a');
        if (!linkElement) return;
        const link = linkElement.getAttribute('href');
        if (isLocalUrl(link) || isWhitelistedUrl(link)) return;
        e.preventDefault();
        const confirmation = await confirmationFn(link);
        if (confirmation) window.open(link);
    });
};

// replace confirmationFn with your custom handler which returns Promise
confirmExternalLinks((link) => confirm(`Proceed to ${link}?`));