# Hyphen inside sets in JavaScript regex

The hyphen is also a special character inside `[ ]` (but not outside). If you need the hyphen itself as a regular character - then put it where it will not be interpreted as a group separator.

Why it's important: You can make a group of characters without yourself noticing it. For example, like this - `'[:-@]'` - you think you are choosing a colon, a hyphen and an AT symbol, but in fact you get a group of characters between `:` and `@`. This group includes the following characters: `? < = > : ;`

Where are they from? From the table ASCII - the colon has a number less than the an AT - and the result is a group. That is, all groups are obtained according to the ASCII table (if desired, you can use this).

How to deal with this: put a hyphen character where it will definitely not be perceived as a group character, for example, at the beginning or at the end (i.e. after `[` or before `]`).

You can also escape the hyphen - then it will denote itself, regardless of position. For example, instead of `[:-@]` write `[:\-@]` - and there will be no more group, but there will be three characters - a colon, a hyphen and an AT `@`.

## Example

In the following example, the search pattern is: digit `1`, then a letter from `'a'` to `'z'`, then digit `2`:

`let str = '1a2 1-2 1c2 1z2'; let res = str.replace(/1[a-z]2/g, '!');`

As a result, the following will be written to the variable:

`'! 1-2 ! !'`

## Example

Let's now escape the hyphen. The resulting search pattern is: digit `1` followed by letter `'a'` or hyphen or letter `'z'` followed by digit `2`:

`let str = '1a2 1-2 1c2 1z2'; let res = str.replace(/1[a\-z]2/g, '!');`

As a result, the following will be written to the variable:

`'! ! 1c2 !'`

## Example

You can just rearrange the hyphen without escaping it:

`let str = '1a2 1-2 1c2 1z2'; let res = str.replace(/1[az-]2/g, '!');`

As a result, the following will be written to the variable:

`'! ! 1c2 !'`

## Example

In the following example, the search pattern is: the first character is small letters or a hyphen `'-'`, then two letters `'x'`:

`let str = 'axx Axx -xx @xx'; let res = str.replace(/[a-z-]xx/g, '!');`

As a result, the following will be written to the variable:

`'! Axx ! @xx'`

## Example

In the following example, the search pattern is: the first character is small, capital letters or a hyphen `'-'`, then two letters `'x'`:

`let str = 'axx Axx -xx @xx'; let res = str.replace(/[a-zA-Z-]xx/g, '!');`

As a result, the following will be written to the variable:

`'! ! ! @xx'`

## Example

You can place a hyphen between two groups - there it definitely won't make one more group:

`let str = 'axx 9xx -xx @xx'; let res = str.replace(/[a-z-0-9]xx/g, '!');`

As a result, the following will be written to the variable:

`'! ! ! @xx'`

## Practical tasks

Given a string:

`let str = 'xaz xBz xcz x-z x@z';`

Find all strings with the following pattern: letter `'x'`, capital or small letter or hyphen, letter `'z'`.

Given a string:

`let str = 'xaz x$z x-z xcz x+z x%z x*z';`

Find all strings with the following pattern: letter `'x'`, then either dollar, or hyphen or plus sign, then letter `'z'`.

←→
↑
en ru