const obj = {};
obj.self = obj;
console.log('Simple circular:', obj);
const a = { name: 'a' };
const b = { name: 'b' };
a.b = b;
b.a = a;
console.log('Mutual circular:', a);
const arr = [1, 2, 3];
arr.push(arr);
console.log('Array circular:', arr);