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[Guide] ES6: Prevent object mutation; fixes and enhancements (#34649)

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* [Guide] ES6: Prevent object mutation; fixes and enhancements

- Remove phantom image
- Remove notes for contributors
- Change explanation and hints.
- Links to markdown

* Changed as requested

Changed titles as requested by @randelldawson. 
Note: I'm just used to [MDN](https://developer.mozilla.org/en-US/docs/MDN/Contribute/Guidelines/Writing_style_guide#Page_titles) and other language styles and though it was clearer. Is it ok now for this guide?

* fix: removed repl.it link
This commit is contained in:
Adrian Skar
2019-03-10 19:07:48 +01:00
committed by Randell Dawson
parent 992c39f7a3
commit 97a74b68e8
1 changed files with 6 additions and 19 deletions
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guide/english/certifications/javascript-algorithms-and-data-structures/es6/prevent-object-mutation/index.md
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---
title: Prevent Object Mutation
---
![](//discourse-user-assets.s3.amazonaws.com/original/2X/3/3c8584a085a0deaea66b3400e6321eeadab552a2.jpg)
![:triangular_flag_on_post:](https://forum.freecodecamp.com/images/emoji/emoji_one/triangular_flag_on_post.png?v=3 ":triangular_flag_on_post:") Remember to use <a>**`Read-Search-Ask`**</a> if you get stuck. Try to pair program ![:busts_in_silhouette:](https://forum.freecodecamp.com/images/emoji/emoji_one/busts_in_silhouette.png?v=3 ":busts_in_silhouette:") and write your own code ![:pencil:](https://forum.freecodecamp.com/images/emoji/emoji_one/pencil.png?v=3 ":pencil:")
### Problem Explanation:
We need to prevent `MATH_CONSTANTS` value from changing.
_You need to freeze the `MATH_CONSTANTS` object so that no one is able to alter the value of `PI`, add, or delete properties ._
## ![:speech_balloon:](https://forum.freecodecamp.com/images/emoji/emoji_one/speech_balloon.png?v=3 ":speech_balloon:") Hint: 1
* Use Object.freeze(obj) to prevent object from being changed.
* _Use `Object.freeze()` to prevent mathematical constants from changing._
> _try to solve the problem now_
@ -19,9 +17,9 @@ We need to prevent `MATH_CONSTANTS` value from changing.
![warning sign](//discourse-user-assets.s3.amazonaws.com/original/2X/2/2d6c412a50797771301e7ceabd554cef4edcd74d.gif)
**Solution ahead!**
**Solution Ahead!**
## ![:beginner:](https://forum.freecodecamp.com/images/emoji/emoji_one/beginner.png?v=3 ":beginner:") Basic Code Solution:
## ![:beginner:](https://forum.freecodecamp.com/images/emoji/emoji_one/beginner.png?v=3 ":beginner:") Basic code solution:
```javascript
function freezeObj() {
"use strict";
@ -41,21 +39,10 @@ We need to prevent `MATH_CONSTANTS` value from changing.
const PI = freezeObj();
```
![:rocket:](https://forum.freecodecamp.com/images/emoji/emoji_one/rocket.png?v=3 ":rocket:") <a href='https://codepen.io/dylantyates/pen/OwVxYB' target='_blank' rel='nofollow'>Run Code</a>
# Code Explanation:
By using Object.freeze() on `MATH_CONSTANTS` we can avoid manipulating it.
#### Relevant Links
* <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze' target='_blank' rel='nofollow'>Object.freeze()</a>
## ![:clipboard:](https://forum.freecodecamp.com/images/emoji/emoji_one/clipboard.png?v=3 ":clipboard:") NOTES FOR CONTRIBUTIONS:
* ![:warning:](https://forum.freecodecamp.com/images/emoji/emoji_one/warning.png?v=3 ":warning:") **DO NOT** add solutions that are similar to any existing solutions. If you think it is **_similar but better_**, then try to merge (or replace) the existing similar solution.
* Add an explanation of your solution.
* Categorize the solution in one of the following categories — **Basic**, **Intermediate** and **Advanced**. ![:traffic_light:](https://forum.freecodecamp.com/images/emoji/emoji_one/traffic_light.png?v=3 ":traffic_light:")
* Please add your username only if you have added any **relevant main contents**. (![:warning:](https://forum.freecodecamp.com/images/emoji/emoji_one/warning.png?v=3 ":warning:") **_DO NOT_** _remove any existing usernames_)
> See ![:point_right:](https://forum.freecodecamp.com/images/emoji/emoji_one/point_right.png?v=3 ":point_right:") <a href='http://forum.freecodecamp.com/t/algorithm-article-template/14272' target='_blank' rel='nofollow'>**`Wiki Challenge Solution Template`**</a> for reference.
### Resources
- ["Object.freeze()" - *MDN Javascript reference*](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze)