freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/regular-expressions/reuse-patterns-using-capture-groups/index.md

---
title: Reuse Patterns Using Capture Groups
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# Reuse Patterns Using Capture Group


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## Hints

### Hint 1
Given code below:
```javascript
let testString = "test test test";
let reRegex = /(test)\s\1/;
let result = reRegex.test(testString);
```
`result` will match only `test test` because `\1` in this example stands for the same text as most recently matched by the 1st capturing group `(test)`.

If we were to literally translate the regex, it would look something like this:

```js
let re = /(test)\s\1/;
let literalRe = /test\stest/;
```
Both `re` and `literalRe` would match the same thing.

### Hint 2
Given the code below:
```javascript
let testString = "test test test";
let reRegex = /(test)(\s)\1\2\1/;
let result = reRegex.test(testString);
```
`result` will match whole `test test test` because:
`\1` repeats (test)
`\2` repeats (\s)

### Hint 3
The code below:
```javascript
let testString = "test test test test test test";
let reRegex = /(test)(\s)\1\2\1/g;
let result = reRegex.test(testString);
```
because we used `\g`, our Regex doesn't return after first full match (`test test test`) and matched all repetitions.


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## Solutions

<details><summary>Solution 1 (Click to Show/Hide)</summary>

```javascript
let repeatNum = "42 42 42";
let reRegex = /^(\d+)\s\1\s\1$/;
let result = reRegex.test(repeatNum);
```

</details>