cat_weight_scale.js

function doGet(e) {
  var now = new Date();
  var sheet = getSheetOfDate(now);
  var rawWeightFrom = e && e.parameter && e.parameter.raw_weight_from;
  var rawWeightTo = e && e.parameter && e.parameter.raw_weight_to;
  var etc = e && e.parameter && e.parameter.etc;
  
  var response;
  if (rawWeightTo) {
    // https://stackoverflow.com/a/17637159
    var avals = sheet.getRange("A1:A").getValues();
    var nextRow = avals.filter(String).length + 1;
    sheet.getRange(nextRow, 1).setValue(now);
    sheet.getRange(nextRow, 2).setValue(rawWeightFrom);
    sheet.getRange(nextRow, 3).setValue(rawWeightTo);
    sheet.getRange(nextRow, 4).setValue(etc);
    response = { status: 'success' };
  } else {
    response = { status: 'failed', message: 'Parameter raw_weight is missing' };
  }

  var output = ContentService.createTextOutput();
  output.setMimeType(ContentService.MimeType.JSON);
  output.setContent(JSON.stringify(response));
  return output;
}

function getSheetOfDate(date) {
  var ymd = getNowYMD(date);
  var spreadsheet = SpreadsheetApp.getActive();
  var sheets = spreadsheet.getSheets();
  var sheet = null;
  for (var i=0;i<sheets.length;i++) {
    if (sheets[i].getName() == ymd) {
      sheet = sheets[i];
      break;
    }
  }
  if (sheet == null) {
    sheet = spreadsheet.insertSheet();
    sheet.setName(ymd);
    sheet.getRange(1, 1).setValue('timestamp');
    sheet.getRange(1, 2).setValue('raw_weight_from');
    sheet.getRange(1, 3).setValue('raw_weight_to');
    sheet.getRange(1, 4).setValue('etc');
    var columns = sheet.getMaxColumns();
    if (columns > 10) {
      sheet.deleteColumns(10, columns - 10)
    }
  }
  return sheet;
}

function getNowYMD(date) {
  var y = date.getFullYear();
  var m = ("00" + (date.getMonth()+1)).slice(-2);
  var d = ("00" + date.getDate()).slice(-2);
  var result = y + "-" + m;
  return result;
}