JavaScript Document domain Property

const currentDomain = document.domain;
console.log(currentDomain);
// e.g. "developer.mozilla.org" on MDN

const currentHostname = location.hostname;
console.log(currentHostname);
console.log(document.domain === location.hostname);

try {
  // Not a parent of the current hostname → should fail
  document.domain = "not-a-parent.example";
  console.log("unexpected: set succeeded");
} catch (err) {
  console.log(err.name);  // "SecurityError"
}
console.log("Prefer postMessage — do not use the setter");