freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/es6/declare-a-read-only-variable-with-the-const-keyword/index.md

---
title: Declare a Read-Only Variable with the const Keyword
---
![](//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:

Change all the variables to `let` or `const` and rename `sentence`.

## ![:speech_balloon:](https://forum.freecodecamp.com/images/emoji/emoji_one/speech_balloon.png?v=3 ":speech_balloon:") Hint: 1

*   Replace `var` for string with read-only `const`.

> _try to solve the problem now_

## ![:speech_balloon:](https://forum.freecodecamp.com/images/emoji/emoji_one/speech_balloon.png?v=3 ":speech_balloon:") Hint: 1

*   Replace `var` in `for` loop to `let`.

> _try to solve the problem now_

## ![:speech_balloon:](https://forum.freecodecamp.com/images/emoji/emoji_one/speech_balloon.png?v=3 ":speech_balloon:") Hint: 1

*   Common convention is to name `const` variables with ALL CAPS.

> _try to solve the problem now_

## Spoiler Alert!

![warning sign](//discourse-user-assets.s3.amazonaws.com/original/2X/2/2d6c412a50797771301e7ceabd554cef4edcd74d.gif)

**Solution ahead!**

## ![:beginner:](https://forum.freecodecamp.com/images/emoji/emoji_one/beginner.png?v=3 ":beginner:") Basic Code Solution:
```javascript
    function printManyTimes(str) {
      "use strict";
      const SENTENCE = str + " is cool!";
      for (let i = 0; i < str.length; i+=2) {
        console.log(SENTENCE);
      }
    }
    printManyTimes("freeCodeCamp");
```
![:rocket:](https://forum.freecodecamp.com/images/emoji/emoji_one/rocket.png?v=3 ":rocket:") <a href='https://codepen.io/dylantyates/pen/OwVxyx' target='_blank' rel='nofollow'>Run Code</a>

# Code Explanation:

By using `const` on `sentence` we can make it read-only and by using `let` on `i` inside the for loop we can avoid using `var` all together. For added code clarity we can also change `sentence` to `SENTENCE` to show that it is a constant.

#### Relevant Links

*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/const' target='_blank' rel='nofollow'>const</a>
*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let' target='_blank' rel='nofollow'>let</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:")