What is wrong with this JavaScript foreach loop?

var videos = {
    a: Popcorn("#a"),
    b: Popcorn("#b"),
    c: Popcorn("#c")
}

videos.forEach(function(vid){
    if (vid.media.readyState === 4) {
    vid.currentTime(
      videos.a.currentTime()
    );
  }
}); 

For some context, I am attempting to scale-up this JSFiddle: Synchronizing Playback of Two Videos so that I can play any number of videos simultaneously.

In addition, I am wondering if there is any way to apply the foreach loop to each element in the array EXCEPT for the element in the 0th index.

Objects don't have forEach Method, instead you can create array of object keys & loop through the keys to access all keys & check values like this

Object.keys(videos).forEach((vid)=>{
    if (videos[vid].media.readyState === 4) {
        videos[vid].currentTime(
          videos.a.currentTime()
        );
      }
});