const a = { x: 1 };
a.__proto__.x = 2;
const b {};

console.log(a.x, b.x);

class CustomError extends Error {
  constructor(message) {
    super(message);
    this.name = 'CustomError';
  }
}

try {
  try {
    throw new CustomError('inner error');
  } catch (e) {
    console.log(e.name);
    throw new Error('outer error');
  }
} catch (e) {
  console.log(e.message);
  console.log(e instanceof CustomError);
}