@stdlib/assert/is-whitespace/README.md

Standard assertion utilities.

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# isWhitespace

> Test whether a string contains only [white space][whitespace] characters.

<section class="usage">

## Usage

```javascript
var isWhitespace = require( '@stdlib/assert/is-whitespace' );
```

#### isWhitespace( value )

Tests whether a string contains only [white space][whitespace] characters.

```javascript
var bool = isWhitespace( '             ' );
// returns true
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   A [white space][whitespace] character is defined as one of the 25 characters defined as a [white space][whitespace] ("WSpace=Y","WS") character in the Unicode 9.0 character database, as well as one related [white space][whitespace] character without the Unicode character property "WSpace=Y" (zero width non-breaking space which was deprecated as of Unicode 3.2).
-   For non-string values, the function returns `false`.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var isWhitespace = require( '@stdlib/assert/is-whitespace' );

var out = isWhitespace( '              ' );
// returns true

out = isWhitespace( '' );
// returns false

out = isWhitespace( '\\r\\n' );
// returns false

out = isWhitespace( 123 );
// returns false
```

</section>

<!-- /.examples -->

* * *

<section class="cli">

## CLI

<section class="usage">

### Usage

```text
Usage: is-whitespace [options] [<string>]

Options:

  -h,    --help                Print this message.
  -V,    --version             Print the package version.
         --split sep           Delimiter for stdin data. Default: '/\\r?\\n/'.
```

</section>

<!-- /.usage -->

<!-- CLI usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

### Notes

-   If the split separator is a [regular expression][mdn-regexp], ensure that the `split` option is either properly escaped or enclosed in quotes.

    ```bash
    # Not escaped...
    $ echo -n $'   \nboop' | is-whitespace --split /\r?\n/

    # Escaped...
    $ echo -n $'   \nboop' | is-whitespace --split /\\r?\\n/
    ```

-   The implementation ignores trailing delimiters.

</section>

<!-- /.notes -->

<section class="examples">

### Examples

```bash
$ is-whitespace foo
false
```

To use as a [standard stream][standard-streams],

```bash
$ echo -n 'foo' | is-whitespace
false
```

By default, when used as a [standard stream][standard-streams], the implementation assumes newline-delimited data. To specify an alternative delimiter, set the `split` option.

```bash
$ echo -n '   \tbar' | is-whitespace --split '\t'
true
false
```

</section>

<!-- /.examples -->

</section>

<!-- /.cli -->

<!-- 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/regexp/whitespace`][@stdlib/regexp/whitespace]</span><span class="delimiter">: </span><span class="description">return a regular expression to match a white space character.</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">

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

[standard-streams]: https://en.wikipedia.org/wiki/Standard_streams

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

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

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

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

</section>

<!-- /.links -->