youtube-to-invidious/background.js

// Storage init
browser.runtime.onInstalled.addListener(function() {
  browser.storage.sync.set({
    url: "https://invidious.snopyta.org"
  });
});


// Url format
function getVideoToken(url) {
  // https://regexr.com/531i0
  var rx = /(?:\/|%3D|v=|vi=)([0-9A-z-_]{11})(?:[%#?&]|$)/g;
  var arr = rx.exec(url);
  return arr[1]; 
}

function cleanToken(token) {
  let t = token;
  // https://regexr.com/531i0
  t = t.replace(/^(vi=|v=)/,"");
  t = t.replace(/^(\/)/,"");
  t = t.replace(/^(%3D)/,"");
  t = t.replace(/(&|%)$/,"");
  return t;
}


// Links click event handling
browser.runtime.onMessage.addListener(function(message) {
  let url = message.url;
  const name = message.targetName;
  browser.storage.sync.get("url").then(function(item) {
    const subst = item.url + `/watch?v=`;
    let token = getVideoToken(url)
    const cleanedToken = cleanToken(token)
    url = url.replace(/.*\/watch\?v=/gm, subst);

    if (name != "_self") {
      browser.tabs.create(
        {active: true, url: url}
      );
    } else {
      browser.tabs.update(
        {url: url, loadReplace: false}
      )
    }
    console.log('Youtube to invidious is redirecting you to invidious')
  })
});