Google App Script to get a daily e-mail of all new comments from a specific YouTube playlist.

getCommentsFromPlaylist.js

function myFunction() {
  var playlistID = "[PLALIST ID GOES HERE]"
  var APIKey = "[GET AN API KEY FROM GOOGLE TO GO HERE]"
  var toEmail = "[E-MAIL OF COMMENTS WILL BE SENT TO THIS ADDRESS]"
  
  var channelIds = [];  
  var message = "";
  var totalPlaylistViews = 0;
  var TIME_LENGTH = 60 * 60 * 1000 * 24.5; // Will get all comments from the last 24.5 hours
  var scriptProperties = PropertiesService.getScriptProperties();
  
  // These next few variables are to help determine how many views per day
  var firstDayOfVideos = new Date(2017, 1, 8);
  var today = new Date();
  var numberOfDaysSinceFirstDay = Math.floor((today.getTime() - firstDayOfVideos.getTime()) / (1000 * 60 * 60 * 24));
  
  // Get list of videos on playlist
  var playlist = UrlFetchApp.fetch("https://www.googleapis.com/youtube/v3/playlistItems?part=snippet&maxResults=50&playlistId=" + playlistID + "&key=" + APIKey);  
  var playlistDetails = JSON.parse(playlist).items
  
  // Get comments on each video on the playlist
  playlistDetails.forEach(function(element) {
    var videoID = element.snippet.resourceId.videoId;
    var videoTitle = element.snippet.title;
    var commentList = UrlFetchApp.fetch("https://www.googleapis.com/youtube/v3/commentThreads?part=snippet&maxResults=20&videoId="+ videoID +"&key=" + APIKey);
    var commentDetails = JSON.parse(commentList).items
    
    // Get view count on each video
    var videoStatistics = UrlFetchApp.fetch("https://www.googleapis.com/youtube/v3/videos?part=statistics&id="+ videoID +"&key=" + APIKey);
    totalPlaylistViews += parseInt(JSON.parse(videoStatistics).items[0].statistics.viewCount)
    
    // Add each comment to the message body of the e-mail
    commentDetails.forEach(function(commentElement) {
      var commentTime = new Date(commentElement.snippet.topLevelComment.snippet.updatedAt);
      var commentElement = commentElement

      if (((new Date) - commentTime) < TIME_LENGTH) {
        var commentText = commentElement.snippet.topLevelComment.snippet.textDisplay;
        message += commentText + "<br><i>From video <a href='https://www.youtube.com/watch?v=" + videoID + "'>" + videoTitle + "</a></i><br>-----------------------<br><br>";
      };
    });
    
  });
  
  // Add view counts at the end of the message
  var viewsSinceYesterday = totalPlaylistViews - (scriptProperties.getProperty('YESTERDAY_VIEWS'));
  message += "Total Playlist Views: " + totalPlaylistViews + 
    "<br>Views in last 24 hours: " + viewsSinceYesterday + 
    "<br>Average views per day since beginning: " + Math.floor((totalPlaylistViews / numberOfDaysSinceFirstDay));
  
  scriptProperties.setProperty('YESTERDAY_VIEWS', totalPlaylistViews); // Set YESTERDAY_VIEWS for use when script runs tomorrow

  // Send e-mail
  MailApp.sendEmail({
    to: toEmail,
    subject: "Daily Comments",
    htmlBody: message,
  });
}