RSSFinder/rssfinder/finder.js

(function() {

var availableLinks = [];
var links = document.getElementsByTagName('link');
var siteTitle = 'No title was found';

if (document.getElementsByTagName('title').lenght > 0) {
    siteTitle = document.getElementsByTagName('title')[0].innerHTML
}

for (link of links) {
    if (   (link.getAttribute('rel') == 'alternate')
        && (   (link.getAttribute('type') == 'application/rss+xml')
            || (link.getAttribute('type') == 'application/atom+xml')
            || (link.getAttribute('type') == 'application/stream+json')
            || (link.getAttribute('type') == 'application/rdf+xml')
        )
    ) {
        var linkTitle;
        var linkUrl;

        if (link.hasAttribute('title')) {
            linkTitle = link.getAttribute('title');
        } else {
            linkTitle = siteTitle;
        }

        if (link.hasAttribute('href') == true) {
            if (link.getAttribute('href').startsWith('/')) {
                linkUrl = window.location.protocol + '//' + window.location.hostname + link.getAttribute('href');
            } else if (!link.getAttribute('href').includes('/')) {
                linkUrl = window.location.protocol + '//' + window.location.hostname + '/' + link.getAttribute('href');
            } else {
                linkUrl = link.getAttribute('href');
            }

            availableLinks.push({
                title: linkTitle,
                url: linkUrl
            });
        }
    }
}

if (availableLinks.length == 0) {
    availableLinks.push({
        title: 'No RSS feed was found',
        url: 'No URL is provided'
    });
}

var out = {
    links: availableLinks
};

return out;

})()