Utility functions for AppScript from Google for Sheets. Taken from: https://community.appsheet.com/t/introducing-script-nuggets/41515

appScriptNuggets.js

*
          NAME: SCRIPT NUGGETS 
   DESCRIPTION: Apps Script functions for use with AppSheet
         SETUP: Replace YOUR_SHEET_ID in first line with the sheet Id from the sheet URL
            BY: GreenFlux, LLC

*//////////////////////////////////////////////////////////////////////////////////////////////////////

const ss = SpreadsheetApp.openById('YOUR_SHEET_ID');//(id from sheetURL)

// ----- TEST WRAPPERS()        {  sourceFunction(parameters);                        (parameter names)
// ====================================================================================================
function maxIdFromColNameTEST() {maxIdFromColName('invoice', 'number')};           // (shName, colName) 
function maxIdFromColNumTEST()  { maxIdFromColNum('invoice', '2')};                // (shName, colNum )
function colNumFromNameTEST()   {  colNumFromName('invoice', 'created_at')};       // (shName, colName)
function clearSheetTEST()       {      clearSheet('Test')};                        // (shName, colName)
function rowToObjTEST()         {        rowToObj('customer', '2')};               // (shName, colName)
function latestFileTEST()       {      latestFile('FOLDER_ID')}; //  (folderId)
function imgToBase64TEST()      {     imgToBase64('FILE_ID')}; //    (fileId)
function getFileURLTEST()       {      getFileURL('FILE_ID')}; //    (fileId)
// ====================================================================================================
///////////////////////////////////////////////////////////////////////////////////////////////////////
function clearSheetFormat() {
  var allSheets = ss.getSheets();
  
  for (var s in allSheets){
    var lastCol = allSheets[s].getLastColumn();
    allSheets[s].clearFormats();
    allSheets[s].setFrozenRows(0);
  }
}

////////////////////////////////////////////////////////////////////////////////
function formatSheets() {
  var allSheets = ss.getSheets();
  
  for (var s in allSheets){
    var lastCol = allSheets[s].getLastColumn();
    allSheets[s].setFrozenRows(1);
    allSheets[s].getRange(1, 1, 1, lastCol).setFontWeight("bold");
  }
}

////////////////////////////////////////////////////////////////////////////////
function colNumFromName(shName, colName){
  var sh = ss.getSheetByName(shName);
  var headerArr = sh.getRange(1, 1, 1, sh.getLastColumn()).getValues()[0];
  for (var i = 0; i < headerArr.length; i++) {
    if (headerArr[i] == colName) {
      i = i + 1; // array loop starts at zero, ColNum starts at one
      Logger.log(i);
      return i ; // the column number for colName in shName
    }
  }
}

////////////////////////////////////////////////////////////////////////////////
function maxIdFromColNum(shName, colNum) {
  var sh = ss.getSheetByName(shName);
  if (sh.getLastRow() > 1) {
    var colArr = sh.getRange(2, colNum, sh.getLastRow(), 1).getValues();
    var maxInColumn = colArr.sort(function(a, b){return b-a})[0][0] ;
  }
  else maxInColumn = "";
  var maxId = 0;
  if (maxInColumn != "") {maxId = maxInColumn};
  Logger.log(maxId);
  return maxId
}

////////////////////////////////////////////////////////////////////////////////
function maxIdFromColName(shName, colName) {  
  var colNum = colNumFromName(shName, colName);
  var maxId  = maxIdFromColNum(shName, colNum);
  Logger.log(maxId);
  return maxId
}

////////////////////////////////////////////////////////////////////////////////
function clearSheet(sheetName) {
  var cSheet  = ss.getSheetByName(sheetName);
  var lastRow = cSheet.getLastRow();
  var lastCol = cSheet.getLastColumn();
  cSheet.getRange(2, 1, lastRow, lastCol).clear();
}

////////////////////////////////////////////////////////////////////////////////
function sheetsToObj() {
  var sheets = ss.getSheets();
  var body   = {};
  
  for(i=0;i<sheets.length;i++){
    var shName   = sheets[i].getName();
    var sh_i     = ss.getSheetByName(shName);
    body[shName] = sh_i.getRange(1, 1, 1, sh_i.getLastColumn()).getValues();
  };
  Logger.log(JSON.stringify(body, null, 2));
  return body;
};

////////////////////////////////////////////////////////////////////////////////
function rowToObj(shName, rowNum) {
  var sh      = ss.getSheetByName(shName);
  var headers = sh.getRange(1, 1, 1, sh.getLastColumn()).getValues()[0];
  var rowData = sh.getRange(rowNum, 1, 1, sh.getLastColumn()).getValues()[0];
  var body    = {};
  
  for(var i = 0;i<headers.length;i++){
    body[headers[i]] = rowData[i];
  };
  
  Logger.log(JSON.stringify(body, null, 2));
  return body
}

////////////////////////////////////////////////////////////////////////////////
function latestFile(folderId) {
  var gFolder = DriveApp.getFolderById(folderId);  //id string from URL of image folder
  var files   = gFolder.getFiles();
  var result  = [];
  do {
    var file = files.next();
    result.push([file.getDateCreated(), file.getId()]);
  } while (files.hasNext()) ;
  result.sort();
  result.reverse();
  var id = result[0][1];
  Logger.log(id);
  Logger.log(result);
  return id;// return most recent file ID in gFolder
}

////////////////////////////////////////////////////////////////////////////////
function imgToBase64(fileId){
  try{
    var file = DriveApp.getFileById(fileId); 
    var data = Utilities.base64Encode(file.getBlob().getBytes());
  }catch(err){Logger.log(err)}
  finally{    
    Logger.log(data);
    return data;
  }
}

////////////////////////////////////////////////////////////////////////////////
function getFileURL(fileId){
  var fileURL = 'https://drive.google.com/uc?export=view&id=' + fileId;
  var html = '<img src = "' + fileURL + '">'; 
  Logger.log(fileURL);
  return fileURL;
};