youtube_get_video_id_list.js

var contents = ytInitialData.contents.twoColumnWatchNextResults.playlist.playlist.contents;
var videoIdList = [];
for(var content of contents) {
  try {
    var videoId = content.playlistPanelVideoRenderer.navigationEndpoint.watchEndpoint.videoId
    console.log(videoId);
    videoIdList.push(videoId);
  } catch(e) {
    console.error(e);
  }
}
JSON.stringify(videoIdList);