sendMail.js

function sendMail() {
  var today = new Date();
  var MAIL_TO = "メールアドレス";

  var cycles = (function() {
    var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("サイクル");
    var rows = sheet.getDataRange();
    var numRows = rows.getNumRows();
    var values = rows.getValues();
    return values;
  })();
  
  var logs = (function() {
    var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("購入ログ(商品データ)");
    var rows = sheet.getDataRange();
    var numRows = rows.getNumRows();
    var values = rows.getValues();
    return values;    
  })();
  
  var latestLog = function(asin) {
    for (var i = logs.length - 1; i >= 1; i--) {
      var log = logs[i];
      var log_asin = log[2];
      if (asin == log_asin) {
        return log;
      }
    }
  };
  
  var alerts = [];
  
  for (var i = 1; i < cycles.length; i++) {
    var cycle = cycles[i];
    var url = cycle[0];
    var asin = cycle[1];
    var name = cycle[2];
    var cycle_date = cycle[4];
    var latest = latestLog(asin);
    if (!latest) {
      continue;
    }
    var purchase_date = latest[0];
    var next_purchase_date = new Date((new Date(purchase_date)).getTime() + cycle_date * 24 * 60 * 60 * 1000);
    if (new Date(next_purchase_date) < today) {
      message = name + " は、前回の購入から" + cycle_date + "日以上経っています。そろそろ購入を検討してはいかがですか？\n" + url;
      alerts.push(message);
    }
  }
  
  var formattedToday = Utilities.formatDate(new Date(), "JST", "yyyy-MM-dd");
  
  MailApp.sendEmail(MAIL_TO, "そろそろアラート" + "(" + formattedToday + ")",
                    "お家を快適に保つには、定期的なお手入れ用具の交換が大事です。" + "\n\n" + alerts.join("\n"));

}