a google apps script that runs against a spreadsheet every week and emails me if peeps got a bday coming up

bday_reminder.gs

/*
a script that runs every sunday to let me know of birthdays coming up that week
most of the math happens in the spreadsheet
--> example: https://docs.google.com/spreadsheets/d/1iXcg0THKuQwosKiD5syktAmGA390Gu8OSFs5iKM1EwQ/edit?usp=sharing
*/

function birthdayNotifier() {

  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet = ss.getSheets()[0];
  var range = sheet.getDataRange();
  var rows = selection.getNumRows();

  var days = ['Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday'];
  var recipients = ['[email protected]']
  var bdays_this_week = [];
  var str = '';

  for (var row = 2; row <= rows; row++) {
    var is_this_week = range.getCell(row, 8).getValue();
    var days_till = range.getCell(row, 7).getValue();

    if (is_this_week) {
      var age = range.getCell(row, 4).getValue() + 1;
      if (days_till === 0) {
        age = range.getCell(row, 4).getValue();
      }
      bdays_this_week.push({
        'name': range.getCell(row, 1).getValue() + ' ' + range.getCell(row, 2).getValue(),
        'age_on_bday': age,
        'day_of_week': days[range.getCell(row, 5).getValue().getDay()]
      })
    }
  }

  if (bdays_this_week.length > 0) {
    var subject = 'Birthdays this week (' + bdays_this_week.length + ')';

    if (bdays_this_week.length === 1) {
      subject = 'Birthday this week';
    }

    str += '<h4>Birthdays this week (' + bdays_this_week.length + ')</h4><ul>';

    for (var i = 0; i < bdays_this_week.length; i++) {
      str += '<li>' + bdays_this_week[i].name + ' (' + bdays_this_week[i].age_on_bday + '): ' + bdays_this_week[i].day_of_week + '</li>';
    }
    
    str += '</ul>';
    
    MailApp.sendEmail({
     to: recipients.join(','),
     subject: subject,
     htmlBody: str
   }); 
  }

};