Google Apps Script mail merge

email.html

<p>Dear <?= name ?>,<p>

<p>Congratulation! You won our smartphone giveaway. Your <?= prize ?> will be shipped to you within one month.</p>

Mail merge.csv

mail_merge.gs

function sendEmail() {
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('Mail merge');
  var range = sheet.getRange(2, 1, sheet.getMaxRows() - 1, 5);
  var values = range.getValues();
  var template = HtmlService.createTemplateFromFile('email');
  
  for (var row in values) {
    var rowValues = values[row];
    var rowIndex = parseInt(row) + 2;
    
    // Early termination when no email address found in a row
    if (isCellEmpty(rowValues[0])) {
      return;
    }
    
    // Skip sent row
    if (!isCellEmpty(rowValues[4])) {
      continue;
    }
    
    template.name = rowValues[1];
    template.prize = rowValues[2];
    
    var html = template.evaluate().getContent();
    var subject = rowValues[1] + ', you are the winner!'
    GmailApp.createDraft(rowValues[0], subject, html, {
      htmlBody: html
    });
    
    // Write the user's email address and timestamp to that row
    sheet.getRange(rowIndex, 4).setValue(Session.getActiveUser().getEmail());
    sheet.getRange(rowIndex, 5).setValue(new Date());
  }
}

// Returns true if the cell where cellData was read from is empty.
// Arguments:
//   - cellData: string
function isCellEmpty(cellData) {
  return typeof(cellData) == "string" && cellData == "";
}