@stdlib/utils/escape-regexp-string/README.md

Standard utilities.

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# rescape

> Escape a [regular expression][mdn-regexp] string or pattern.

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## Usage

```javascript
var rescape = require( '@stdlib/utils/escape-regexp-string' );
```

#### rescape( str )

Escapes a [regular expression][mdn-regexp] `string` or pattern.

```javascript
var str = rescape( '/[A-Z]*/' );
// returns '/\\[A\\-Z\\]\\*/'

str = rescape( '[A-Z]*' );
// returns '\\[A\\-Z\\]\\*'
```

If provided a value which is not a primitive `string`, the function **throws** a `TypeError`.

```javascript
try {
    rescape( null );
    // throws an error...
} catch ( err ) {
    console.error( err );
}
```

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-   The following characters have special meaning inside of regular expressions and need to be escaped in case the characters should be treated literally:

    | description   | value    |
    | ------------- | -------- |
    | Backslash     | `&#92;`  |
    | Braces        | `{ }`    |
    | Brackets      | `[ ]`    |
    | Caret         | `^`      |
    | Dollar Sign   | `$`      |
    | Forward Slash | `/`      |
    | Asterisk      | `*`      |
    | Parentheses   | `( )`    |
    | Period        | `.`      |
    | Plus Sign     | `+`      |
    | Vertical Bar  | `&#124;` |
    | Question Mark | `?`      |

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## Examples

<!-- eslint-disable no-useless-escape -->

<!-- eslint no-undef: "error" -->

```javascript
var rescape = require( '@stdlib/utils/escape-regexp-string' );

var out = rescape( '/beep/' );
// returns '/beep/'

out = rescape( 'beep' );
// returns 'beep'

out = rescape( '/[A-Z]*/' );
// returns '/\\[A\\-Z\\]\\*/'

out = rescape( '[A-Z]*' );
// returns '\\[A\\-Z\\]\\*'

out = rescape( '/\\\//ig' );
// returns '/\\\\\\\//ig'

out = rescape( '\\\/' );
// returns '\\\\\\\/'

out = rescape( '/[A-Z]{0,}/' );
// returns '/\\[A\\-Z\\]\\{0,\\}/'

out = rescape( '[A-Z]{0,}' );
// returns '\\[A\\-Z\\]\\{0,\\}'

out = rescape( '/^boop$/' );
// returns '/\\^boop\\$/'

out = rescape( '^boop$' );
// returns '\\^boop\\$'

out = rescape( '/(?:.*)/' );
// returns '/\\(\\?:\\.\\*\\)/'

out = rescape( '(?:.*)' );
// returns '\\(\\?:\\.\\*\\)'

out = rescape( '/(?:beep|boop)/' );
// returns '/\\(\\?:beep\\|boop\\)/'

out = rescape( '(?:beep|boop)' );
// returns '\\(\\?:beep\\|boop\\)'
```

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[mdn-regexp]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions

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