let buffer = new SharedArrayBuffer(1024);
let arr = new Int32Array(buffer);
arr[0] = 42;

let bc = new BroadcastChannel('channel_name');
bc.onmessage = e => console.log(e.data);
bc.postMessage('سلام از تب دیگه!');

let user = {};
console.log(user?.address?.city); // undefined (بدون ارور)