Get Column Range by Start Row Index, google script for spreadsheets

getcolrange.js

// example usage
function testGetFullColumn()
{
  Logger.log(getFullColumn('A', 1).getNumRows()); // number rows A1:A end
  Logger.log(getFullColumn('B', 2).getNumRows()); // number rows B2:B end
  Logger.log(getFullColumn('C', 5).getNumRows()); // number rows C5:C end
  // also look into:
  // https://developers.google.com/apps-script/storing_data_spreadsheets#reading-2
  // for converting a range into js objects for easier calculations
}

// This function gets the full column Range like doing 'A1:A9999' in excel
// @param {String} column The column name to get ('A', 'G', etc)
// @param {Number} startIndex The row number to start from (1, 5, 15)
// @return {Range} The "Range" object containing the full column: https://developers.google.com/apps-script/class_range
function getFullColumn(column, startIndex){
  var sheet = SpreadsheetApp.getActiveSpreadsheet();
  var lastRow = sheet.getLastRow();
  return sheet.getRange(column+startIndex+':'+column+lastRow);
}