Notify specific web page periodically using GAS

notifyIssues.js

function notifyIssues() {
  var issueurl = PropertiesService.getScriptProperties().getProperty("issueurl");
  var toaddress = PropertiesService.getScriptProperties().getProperty("mailaddress");
  var httpuser = PropertiesService.getScriptProperties().getProperty("httpuser");
  var httppass = PropertiesService.getScriptProperties().getProperty("httppassword");
  var subject = PropertiesService.getScriptProperties().getProperty("subject");
  var header = PropertiesService.getScriptProperties().getProperty("header");
  var passenc = Utilities.base64Encode(httpuser + ":" + httppass);
  var response = UrlFetchApp.fetch(issueurl, {"headers": {"Authorization": "Basic " + passenc}});
  var content = response.getContentText();
  
  var bodyIndex = content.indexOf("wiki-body");
  var listIndex = content.indexOf("<hr", bodyIndex) + 6;
  var bodyEnd = content.indexOf("</div>", listIndex);
  var listContent = content.substring(listIndex, bodyEnd).trim();
  if (listContent && listContent.length > 0) {
    // send mail
    MailApp.sendEmail(toaddress, "", subject, header + listContent + "<p><a href=\"" + issueurl + "\">" + issueurl + "</a></p>");
  }
}