cacheGoogleSheetNotesAndFormulas.js

// ?id=<GOOGLE_SHEET_ID>
function doGet(request) {
  if (!request.parameter.id) {
    return ContentService.createTextOutput(JSON.stringify(new Error('no Google Sheet id set')))
      .setMimeType(ContentService.MimeType.JSON);
  }
  
  var cache = cacheNotesAndFormulas(request.parameter.id);
  
  // Return cache as JSON
  return ContentService.createTextOutput(JSON.stringify(cache))
    .setMimeType(ContentService.MimeType.JSON);
}

function cacheNotesAndFormulas(spreadsheetId) {
  return SpreadsheetApp
    .openById(spreadsheetId)
    .getSheets()
    .reduce(function(cache, sheet) {
      var sheetData = cache[sheet.getName()] = {};
      var range = sheet.getDataRange();
      
      sheetData.range = range.getA1Notation();
      sheetData.notes = range.getNotes();
      sheetData.formulas = range.getFormulas();
      
      return cache;
    }, {});
}