Hint
Map keys use Object.is (reference equality) for objects. Two objects that look equal are different keys unless they're the same reference.
const map = new Map();
const key1 = { id: 1 };
const key2 = { id: 1 };
map.set(key1, 'value1');
map.set(key2, 'value2');
console.log(map.size);
console.log(map.get(key1));
console.log(map.get({ id: 1 }));2 value1 undefined
Explanation: key1 and key2 look the same but are different object references. Map uses reference equality (Object.is) for object keys. Two separate entries. A new { id: 1 } object has no match — returns undefined.
Key Insight: Map keys use Object.is (reference equality) for objects. Two objects that look equal are different keys unless they're the same reference.