takeovercast.user.js

// ==UserScript==
// @name         Take Over(cast)
// @version      0.1
// @namespace    https://davegoesthedistance.com
// @description  Convert Apple Podcast links to Overcast links.
// @author       David Millar
// @match        *://*/*
// @run-at       document-end
// @run-at       document-idle
// ==/UserScript==

(function() {
    'use strict';

    document.addEventListener("DOMContentLoaded", replaceLinks, false );

    if( document.readyState === "complete" ) {
        replaceLinks();
    }

    function checkLink(a) {
        var linkCheck = a.href.toString().match(/itunes\.apple\..*\/.*\/podcast\/.*\/?id(\d+)/i);
        if (linkCheck && linkCheck[1]) {
            a.href = 'https://overcast.fm/itunes' + linkCheck[1];
            if (a.textContent.match(/itunes|apple/ig)) {
                a.textContent = a.textContent.replace(/itunes|apple/ig, 'Overcast');
            }
        }
    }

    function replaceLinks() {
        Array.forEach(document.links, checkLink);
    }

    document.body.addEventListener('mousedown', function(e) {
        if (e.target.tagName != "A") return;
        checkLink(e.target);
    });
})();