@stdlib/regexp/whitespace/README.md

Regular expressions.

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# reWhitespace

> [Regular expression][regexp] to match a [white space][whitespace] character.

<section class="usage">

## Usage

```javascript
var reWhitespace = require( '@stdlib/regexp/whitespace' );
```

#### reWhitespace( \[options] )

Returns a [regular expression][regexp] to match a [white space][whitespace] character. 

```javascript
var RE_WHITESPACE = reWhitespace();

var bool = RE_WHITESPACE.test( '\n' );
// returns true

bool = RE_WHITESPACE.test( ' ' );
// returns true
```

The function accepts an `options` object with optional properties:

-   **flags**: `string` specifying regular expression [flags][mdn-regexp-flags]. Default: `''`.
-   **capture**: `boolean` indicating whether to create a capture group for the match. Default: `false`.

By default, the function returns a regular expression which does not have any flags specified. To specify [flags][mdn-regexp-flags], set the `flags` option with a list of flags (which may be in any order).

```javascript
var RE_WHITESPACE = reWhitespace({
    'flags': 'gm'
});

var str = 'Hello World!';
var bool = RE_WHITESPACE.test( str );
// returns true

bool = RE_WHITESPACE.test( str );
// returns false
```

By default, the function returns a regular expression which does not capture the part of a string matching the regular expression. To capture matches, set the `capture` option.

```javascript
var RE_WHITESPACE = reWhitespace({
    'capture': true
});
var str = 'Hello World!';
var arr = str.split( RE_WHITESPACE );
// returns [ 'Hello', ' ', 'World!' ]
```

#### reWhitespace.REGEXP

[Regular expression][regexp] to match a [white space][whitespace] character. 

```javascript
var bool = reWhitespace.REGEXP.test( '\n' );
// returns true

bool = reWhitespace.REGEXP.test( '\\n' );
// returns false
```

#### reWhitespace.REGEXP_CAPTURE

[Regular expression][regexp] to capture characters matching a [white space][whitespace] character. 

```javascript
var replace = require( '@stdlib/string/replace' );

var str = 'Duplicate capture';
var out = replace( str, reWhitespace.REGEXP_CAPTURE, '$1$1' );
// returns 'Duplicate  capture'
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   Matches the `25` characters defined as white space ("WSpace=Y","WS") characters in the Unicode `9.0` character database.

-   Matches one related white space character without the Unicode character property "WSpace=Y" (zero width non-breaking space which was deprecated as of Unicode 3.2).

-   The `REGEXP` regular expression is defined as 

    ```text
    /[\u0009\u000A\u000B\u000C\u000D\u0020\u0085\u00A0\u1680\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200A\u2028\u2029\u202F\u205F\u3000\uFEFF]/
    ```

-   The `REGEXP_CAPTURE` regular expression is defined as 

    ```text
    /([\u0009\u000A\u000B\u000C\u000D\u0020\u0085\u00A0\u1680\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200A\u2028\u2029\u202F\u205F\u3000\uFEFF])/
    ```

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error",  stdlib/doctest: "off" -->

```javascript
var reWhitespace = require( '@stdlib/regexp/whitespace' );

var RE_WHITESPACE = reWhitespace();

var bool = RE_WHITESPACE.test( 'beep boop' );
// returns true

bool = RE_WHITESPACE.test( '\n' );
// returns true

bool = RE_WHITESPACE.test( '\r' );
// returns true

bool = RE_WHITESPACE.test( '\t' );
// returns true

bool = RE_WHITESPACE.test( 'beep' );
// returns false

var str = 'This is\na newline\r\ndelimited string.';

var arr = str.split( RE_WHITESPACE );
// returns [ 'This', 'is', 'a', 'newline', '', 'delimited', 'string.' ]
```

</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/assert/is-whitespace`][@stdlib/assert/is-whitespace]</span><span class="delimiter">: </span><span class="description">test whether a string contains only white space characters.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

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

[whitespace]: https://en.wikipedia.org/wiki/Whitespace_character

[mdn-regexp-flags]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions#advanced_searching_with_flags_2

<!-- <related-links> -->

[@stdlib/assert/is-whitespace]: https://www.npmjs.com/package/@stdlib/assert-is-whitespace

<!-- </related-links> -->

</section>

<!-- /.links -->