Apa bedane antara shallow copy lan deep copy?

Question

Accepted Answer

Objek didhewe **kanthi referensi**, dadi `b = a` ora nyalin — loro-lorone nuding obyek sing padha. **Shallow copy** ndhuplikat tingkat paling ndhuwur nanging nuduhake referensi nested; **deep copy** ndhuplikat kabeh, sepenuhne independen.

```js
const original = { name: "Ann", address: { city: "NY" } };

// shallow copy: spread / Object.assign
const shallow = { ...original };
shallow.name = "Bob";            // ✅ independent (top-level primitive)
shallow.address.city = "LA";     // ⚠️ ALSO changes original.address.city — shared!

original.address.city; // "LA"  ← mutated through the shallow copy
```

Objek `address` nested iku referensi **sing padha** ing loro, dadi ngowahi iku mengaruhi loro.

## Nggawe deep copy

```js
const deep = structuredClone(original); // modern, built-in, handles most types
deep.address.city = "Chicago";          // ✅ original is untouched
```

Opsi liyane lan caveat-e:

```js
JSON.parse(JSON.stringify(obj)); // simple, but LOSES functions, Dates → strings, undefined
// lodash: _.cloneDeep(obj)       // robust, for complex cases
```

## Mengapa iki penting

Iki sumber paling dhuwur saka bug "kenapa negara saya ngowah ora diduga?" utamane ing React/Redux ing ngendi sampeyan kudu ora ngubah state.

Spread apik nalika sampeyan mung ngganti kolom tingkat dhuwur, nanging kanggo update nested sampeyan kudu nyalin tingkat nested uga (`{ ...obj, address: { ...obj.address, city } }`) utawa nggawe deep clone.