如何确定document.referrer是否来自我自己的网站？

function isReferrerFromSameSite() {
  var currentDomain = window.location.hostname;
  var referrer = document.referrer;
  
  if (referrer) {
    var referrerDomain = extractDomain(referrer);
    return currentDomain === referrerDomain;
  }
  
  return false;
}

function extractDomain(url) {
  var domain;
  // find & remove protocol (http, ftp, etc.) and get domain
  if (url.indexOf("://") > -1) {
    domain = url.split('/')[2];
  }
  else {
    domain = url.split('/')[0];
  }
  // find & remove port number
  domain = domain.split(':')[0];
  return domain;
}