Play embedded Youtube videos for two seconds

youtube-embedded.user.js

// ==UserScript==
// @name     Play embedded Youtube videos for two seconds
// @version  1.0
// @grant    none
// @include  https://www.youtube.com/embed/*
// @include  https://www.youtube-nocookie.com/embed/*
// ==/UserScript==

// I chose two seconds because that's how long the bottom bar with play/pause/time stays visible
// Once that bar disappears, the time won't update, and the script can't react to
// the correct time code. Maybe there's some other way.
var playVideoUntil = "0:02"; 

//wait for the time elapsed timer to count to desired time
var config = { 
  childList: true,
  attributes: true, 
  subtree: true,
  attributeOldValue: true,
  characterData: true
};
var timeElapsedObserver = new MutationObserver(function(mutations) {
  mutations.forEach(function(mutation) {
    console.log(mutation);
    if(mutation.addedNodes.length > 0 
       && mutation.target.innerHTML == playVideoUntil){
      playPauseBtn.click();
    	timeElapsedObserver.disconnect();
    }
  });
});

// big play button in center 
//var playBtn = document.querySelector("button.ytp-large-play-button.ytp-button");
// small play/pause button bottom left
var playPauseBtn = document.querySelector("button.ytp-play-button.ytp-button");

if(playPauseBtn.getAttribute("aria-label") == "Play"){
  playPauseBtn.click();
}

var spanTimeElapsed = document.querySelector("span.ytp-time-current")
timeElapsedObserver.observe(spanTimeElapsed, config);

There seems to be a bug in Greasemonkey for Firefox that prevents this script from working in an <iframe>, see greasemonkey/greasemonkey#2574

Seems to work fine in Chrome with Tampermonkey though.