Suggest an edit

Improve this article

Refine the answer for “structuredClone”. Your changes go to moderation before they’re published.

Approval required

Content

What you’re changing

Title (EN)

Short answer (EN)

Shown above the full answer for quick recall.

Answer (EN)

`structuredClone()` is a **built-in JavaScript function** that makes a **deep copy** of any value, including complex objects, arrays, maps, and even dates.

This is the **most modern and safest way** to clone data in JS without third-party libraries.

---

## In short

```javascript
const clone = structuredClone(value);
```

It creates a **fully independent copy** of the object,
including all nested structures,
and returns a new object with no shared references to the original.

---

## Example

```javascript
const user = {
  name: 'Tim',
  address: { city: 'Berlin' },
  hobbies: ['sport', 'music']
};

const clone = structuredClone(user);

clone.address.city = 'Lviv';
clone.hobbies.push('coding');

console.log(user.address.city); // "Berlin"
console.log(user.hobbies);      // ['sport', 'music']
```

The copy is **deep** -
all nested objects and arrays are recreated.
The original stays unchanged.

---

## What `structuredClone` can copy

Supports:

- objects (`{}`), arrays (`[]`)
- nested structures of any depth
- `Date`
- `Map`, `Set`
- `Blob`, `File`, `ArrayBuffer`, `TypedArray`
- `RegExp` (preserves the pattern and flags)
- even **circular references** (unlike `JSON.stringify()`)

---

### Example with Map and Date

```javascript
const data = {
  date: new Date(),
  map: new Map([['a', 1], ['b', 2]])
};

const copy = structuredClone(data);

console.log(copy.date === data.date); // false (a new object)
console.log(copy.map.get('a'));       // 1
```

---

### Example with a circular reference (it works!)

```javascript
const obj = {};
obj.self = obj;

const clone = structuredClone(obj);
console.log(clone.self === clone); // true
```

`structuredClone()` handles even self-references,
where `JSON.parse(JSON.stringify())` would simply fail with an error.

---

## What is **not copied**

Does not support:

- **functions**
- **DOM elements**
- **classes / prototypes**
- **Symbol**
- **undefined as a key**

```javascript
const obj = {
  fn: () => {},
  el: document.body
};

structuredClone(obj);
// Error: function or DOM node cannot be cloned
```

---

## Comparison with other methods

| Method | Copy type | Copies nested data | Copies functions | Copies Date / Map / Set |
|---|---|---|---|---|
| `{ ...obj }` | shallow | No | Yes | No |
| `Object.assign()` | shallow | No | Yes | No |
| `JSON.parse(JSON.stringify())` | deep | Yes | No | No |
| `structuredClone()` | deep | Yes | No | Yes |
| `_.cloneDeep()` (Lodash) | deep | Yes | No | Yes |

---

## Support

Works:

- in all modern browsers (Chrome 98+, Firefox 94+, Edge 98+, Safari 15.4+)
- in Node.js 17+
- in Deno

For older environments you can add a **polyfill**, for example:

```javascript
npm install core-js
```

---

## SUMMARY

| Property | `structuredClone()` |
|---|---|
| Copy type | Deep |
| Changes the original | No |
| Copies objects, arrays, Map, Set, Date | Yes |
| Works with circular references | Yes |
| Copies functions / DOM elements | No |
| Safe and built-in | Yes |

Markdown · drag & drop images · ⌘B / ⌘I shortcuts470 words

For the reviewer

Note to the moderator (optional)

Visible only to the moderator. Helps review go faster.