PeterBerthelsen

//////////////////////////Reply/Thread////////////////////////////////////////////////////////
  if (IdInResponseTo == 0 || IdInResponseTo == null) {                                      //If no reply is provided...                                                             
    console.log("No reply ID provided.");                                                   //log no reply
  } else {                                                                                  //If Reply (or thread) is set up...
    var ReplyId = IdInResponseTo;                                                           //variable for replies, passed to .sendTweet
    console.log("In response to: " + ReplyId)                                               //log response to   
    params.in_reply_to_status_id = ReplyId;                                                 //send with reply
    params.auto_populate_reply_metadata = true;                                             //auto-mentions previous user (for thread)
  }

PeterBerthelsen

function sendTweet(TweetText, IdInResponseTo, ImageAttachURL){
//////////////////////////Set Variables///////////////////////////////////////////////////////
  var ss = SpreadsheetApp.getActiveSpreadsheet();                                           //spreadsheet  
  var logsheet = ss.getSheetByName("TweetLog");
  var lastRow = Math.max(logsheet.getLastRow(),1) + 1;
  var twitterKeys= {                                                                        //Twitter Authentication Tokens to pass through props
    TWITTER_CONSUMER_KEY: "[YOUR KEY HERE]",
    TWITTER_CONSUMER_SECRET: "[YOUR SECRET HERE]",
    TWITTER_ACCESS_TOKEN: "[YOUR TOKEN HERE]",
    TWITTER_ACCESS_SECRET: "[YOUR SECRET HERE]"