Object values

Objects (including arrays and functions) are reference values. Assignment copies the reference, so two variables can point at the same mutable structure. `{}` === `{}` is false because identity differs even when shape matches.

Property keys are strings or symbols (Map allows any key type). `Object.is(a, a)` checks reference identity. Spread and `Object.assign` make shallow copies — nested objects remain shared.

					const a = { nested: { count: 1 } };
const b = { ...a };
b.nested.count = 2;
console.log(a.nested.count); // 2
				

Prefer Map when keys are not strings/symbols or when you need reliable size and iteration order without prototype pollution.

On interviews, explain the concept with a concrete example and name the runtime behavior interviewers probe.

Common pitfalls include mixing similar APIs and forgetting edge cases during live coding.

The trade-off is often clarity versus performance or safety versus convenience.

Checklist:

• Explain reference assignment.
• Compare object identity with shape equality.
• Call out shallow copy limits.