playlist-extension/content_scripts/content.js

(function () {
  console.log("HELLO FROM PLAYLIST!", Math.floor(Math.random() * 999));

  function msgPlayEvt(type, target) {
    const payload = {
      type,
      url: window.location.href,
      timestamp: target.currentTime,
      duration: target.duration,
      title: document.title.replace(/ - YouTube$/, ""),
    };
    return browser.runtime.sendMessage(payload);
  }

  const vid = document.querySelector("video");

  if (vid) {
    vid.addEventListener("play", function (evt) {
      msgPlayEvt("play", evt.target);
    });
    vid.addEventListener("playing", function (evt) {
      msgPlayEvt("playing", evt.target);
    });
    vid.addEventListener("pause", function (evt) {
      msgPlayEvt("pause", evt.target);
    });
    vid.addEventListener("ended", function (evt) {
      msgPlayEvt("ended", evt.target);
    });
  }

  // Listen for messages from the popup or background script
  browser.runtime.onMessage.addListener((message) => {
    if (message.type === "print") {
      console.log("MESSAGE", message);
    }
    if (message.type === "autoplay") {
      console.log('press play');
      const play = document.querySelector(
        'button.ytp-play-button.ytp-button[data-title-no-tooltip="Play"]',
      );
      if (play) {
        play.click();
      }
    }
  });
})();