# Named capturing groups inside a JavaScript regex

Let's remember how we used capturing groups in a regular expression itself:

`let res = str.replace(/([a-z])\1/g, '!');`

Sometimes there are situations when it is more convenient to refer to a capturing group not by its number, but by its name. To do this, we need to give the capturing group a name:

`let res = str.replace(/(?<letter>[a-z])/g, '!');`

Now we can access to this capturing group with the syntax `\k<name>`, like this:

`let res = str.replace(/(?<letter>[a-z])\k<letter>/g, '!');`

Given a string:

`let str = '12:59:59 12:59:12 09:45:09';`

Find all substrings with time where an hour is the same as a second.

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