# How to clone anything in JavaScript

> Learn how to deep clone anything in JavaScript with structuredClone(), why objects and arrays are copied by reference, and when you still need a polyfill.

Author: Flavio Copes | Published: 2022-12-29 | Canonical: https://flaviocopes.com/how-to-clone-javascript/

We used to do all sorts of stuff in [JavaScript](https://flaviocopes.com/javascript/) land in regards to cloning.

Why?

Because ..references.

Primitive types (strings, numbers, booleans..) are always correctly “cloned” because they are passed by value.

Everything else (objects, arrays, dates, whatever) is an object. And objects are passed by reference.

So we had to do deep cloning using various ways otherwise you end up with the same object reference, under a different name.

But it's 2023 and we can use **structuredClone()**.

```jsx
const b = structuredClone(a)
```

This also deeply clones non-primitive types.

Just pay attention it’s a recent API, so if you use it in the browser make sure you use a build tool that provides core-js (babel) polyfills.