Auto set B cols' formulas.js

/**
 * The onOpen() function, when defined, is automatically invoked whenever the
 * spreadsheet is opened.
 * For more information on using the Spreadsheet API, see
 * https://developers.google.com/apps-script/service_spreadsheet
 */
function onOpen() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var b_col = sheet.getRange('B:B');
  var g_col = sheet.getRange('G:G');
  var num_rows = g_col.getNumRows();
  Logger.log(num_rows);
  var values = g_col.getValues();
  var formulas = [];
  for (var i = 0; i < num_rows; i++){
    Logger.log(values[i][0]);
    formulas[i] = formulas[i] || [];
    if (values[i][0] != ''){
      formulas[i][0] = '=G' + (i+1).toString();
    }else{
      formulas[i][0] = '';
    }
  }
  b_col.setFormulas(formulas);
};

bravo