# JavaScript's copyWithin is strange 😬

I've been writing a comprehensive guide for JavaScript array methods while learning them myself. I tried out all possible variations of each method and the methods were doing what I expected them to do, except for one.

I spent quite some time trying to wrap my head around the `copyWithin` method. Finally, I feel I've got the hang of it now.

Hey there, fellow human of the 'Not-Getting-It' realm! This article? Yep, not for the instant 'I-get-it' champs like you. This one's for us, the brave souls who embrace confusion like a warm hug. So, kick back, relax, and let's dive into the land of 'Huh? Wait, what?' together. Cheers to not getting it on the first try!

# Usage

This method is used to copy a part of the given array and paste that copied content into another location in the same array

# Syntax

```javascript
copyWithin(target, start, end)
```

`target (Required)`\- Where to paste the content to

`start (Optional)`\- Where to start copying the content from **(Default value - 0)**

`end (Optional)`\- Where to finish copying the content (Exclusive) **(Default value - The length of the array)**

# Examples

```javascript
// Example 1 - With only target parameter
let numbers = [90, 88, 33, 77, 5, 66]
numbers.copyWithin(2)
// The same as numbers.copyWithin(2, 0, 6)
console.log(numbers) // [ 90, 88, 90, 88, 33, 77 ]
```

This method,

1. Copies the elements from indexes 0 to 6 (Exclusive), in this case, it is the whole array
    
2. Then it pastes the copied content from index 2 onwards
    

```javascript
// Example 2 - With start and end parameters
let numbers = [15, 18, 22, 40, 65, 35, 58]
numbers.copyWithin(2, 3, 6)
console.log(numbers) // [15, 18, 40, 65, 35, 35, 58]
```

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1692636353244/9d2005db-a4b2-4911-b187-34eee8db5969.png align="center")

```javascript
// Example 3
let numbers = [15, 18, 22, 40, 65, 35, 58]
numbers.copyWithin(5, 3, 6)
console.log(numbers) // [15, 18, 22, 40, 65, 40, 65]
```

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1692636823774/75d4643b-fc63-4be9-a68c-b6d0729cfd62.png align="center")

As you can see, this method **never extends the array**.

If there is not enough space to paste all the copied elements, it will just paste what it can and ignore the rest.

`copyWithin`is in the category of array modification methods. I will provide a comprehensive categorized guide for all the JS Array methods in an upcoming article.

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Thank you for diving into the article! If you found it as captivating as a page-turner, consider dropping a virtual high-five with a like, leaving your thoughts in the comments, and embarking on a journey with me for more mind-enriching content. Until we cross paths again, take care and keep your curiosity alive! 🚀✨