# Why does mosh clone object from an movies array?

**URL:** <https://forum.codewithmosh.com/t/why-does-mosh-clone-object-from-an-movies-array/17382>\
**Category:** React\
**Created:** [January 1, 2023, 11:31pm UTC](https://forum.codewithmosh.com/t/why-does-mosh-clone-object-from-an-movies-array/17382 "2023-01-01T23:31:19Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Dalare](https://avatars.discourse-cdn.com/v4/letter/d/a5b964/32.png) [@Dalare](https://forum.codewithmosh.com/u/Dalare)\
**Post date:** [January 1, 2023, 11:31pm UTC](https://forum.codewithmosh.com/t/why-does-mosh-clone-object-from-an-movies-array/17382/1 "2023-01-01T23:31:19Z")

</div>

**Course : Composing Components**  
**#22-Solution-Like Component**  
**Timeline: 9:12**

```auto
function handleLike(movie) {
    const movies = [...movies];
    const index = movies.indexOf(movie);
    movies[index].like = !movies[index].like; <--- Why clone this object?
    setMovies(movies);
  }

```

I understand the point of cloning first before updating the state but I couldn’t understand why he also cloned that specific object(**movies[index].like = !movies[index].like;**) from the **movies** array because when I run the code without cloning that object in the movies array it works just fine. What am I missing here?

Thank you!

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<div class="post-metadata">

**Author:** ![sufian.babri](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.codewithmosh.com/sufian.babri/32/1028_2.png) [@sufian.babri](https://forum.codewithmosh.com/u/sufian.babri)\
**Post date:** [January 2, 2023, 2:06am UTC](https://forum.codewithmosh.com/t/why-does-mosh-clone-object-from-an-movies-array/17382/2 "2023-01-02T02:06:11Z")

</div>

```auto
movies[index].like = !movies[index].like;

```

This line is simply inverting the value of `like` (changing true to false, and versa). It doesn’t clone anything.

---

<div class="post-metadata">

**Author:** ![maverick](https://avatars.discourse-cdn.com/v4/letter/m/258eb7/32.png) [@maverick](https://forum.codewithmosh.com/u/maverick)\
**Post date:** [January 2, 2023, 4:42am UTC](https://forum.codewithmosh.com/t/why-does-mosh-clone-object-from-an-movies-array/17382/3 "2023-01-02T04:42:24Z")

</div>

> [@Dalare](#):
>
> `movie`

sufian.babri has explained clearly already but I would like to add my explanation as well.

Here is what’s going on:

You can’t use assignment operator to clone objects and arrays (in most programming languages). So, if you use spread operator (…var), you will be able to clone objects easily.

```auto
const movies = [...movies]; // movies from state object is cloned into local movies variable
// get the index of the argument which is a movie object.
const index = movies.indexOf(movie);
movies[index] = {...movies[index]}; // this step was missing. Thanks @SAM. Objects are always assigned by reference so the movie objects inside the cloned array are still pointing to original movie objects.
// this is the line where you got confused: 
// value of like is boolean: true means the movie is liked and false means not liked.
// to achieve this, you will need to check if the current value is true or false and based on that you can update that property.
// so, following is bit lengthy code to achieve that.
if( movies[index].like ) {
    // we will get here only if the movie is liked initially.
    movies[index].like = false;
} else {
    movies[index].like = true;
}
// Note: you can remove above curly braces to make it more clean.
// Mosh refactored above if .. else block to toggle the value of like in single line.
movies[index].like = ! movies[index].like;

...... 

```

This is as comprehensive as it gets.  
Hope this helps.

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<div class="post-metadata">

**Author:** ![Dalare](https://avatars.discourse-cdn.com/v4/letter/d/a5b964/32.png) [@Dalare](https://forum.codewithmosh.com/u/Dalare)\
**Post date:** [January 8, 2023, 2:50am UTC](https://forum.codewithmosh.com/t/why-does-mosh-clone-object-from-an-movies-array/17382/8 "2023-01-08T02:50:50Z")

</div>

My mistake. I forgot to add the 3rd line of code where I was confused with not where you reverse like. Thanks for explaining the entire line of code. Third line was where I wanted explanation. Appreciate your help. 🙂

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<div class="post-metadata">

**Author:** ![Dalare](https://avatars.discourse-cdn.com/v4/letter/d/a5b964/32.png) [@Dalare](https://forum.codewithmosh.com/u/Dalare)\
**Post date:** [January 8, 2023, 2:51am UTC](https://forum.codewithmosh.com/t/why-does-mosh-clone-object-from-an-movies-array/17382/9 "2023-01-08T02:51:47Z")

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Missed the line of code which I wanted to ask but thanks for the help. I learnt from @maverick.