# Constants
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> Standard library constants.
## Installation
```bash
npm install @stdlib/constants
```
## Usage
```javascript
var constants = require( '@stdlib/constants' );
```
#### constants
Standard library constants.
```javascript
var ns = constants;
// returns {...}
```
The constants that are part of this package live in the following sub-namespaces:
- [`array`][@stdlib/constants/array]: array constants.
- [`complex128`][@stdlib/constants/complex128]: 128-bit complex number mathematical constant.
- [`complex64`][@stdlib/constants/complex64]: half-precision floating-point mathematical constants.
- [`float16`][@stdlib/constants/float16]: half-precision floating-point mathematical constants.
- [`float32`][@stdlib/constants/float32]: single-precision floating-point mathematical constants.
- [`float64`][@stdlib/constants/float64]: double-precision floating-point mathematical constants.
- [`int16`][@stdlib/constants/int16]: 16-bit signed integer mathematical constants.
- [`int32`][@stdlib/constants/int32]: 32-bit signed integer mathematical constants.
- [`int8`][@stdlib/constants/int8]: 8-bit signed integer mathematical constants.
- [`path`][@stdlib/constants/path]: standard library string path constants.
- [`time`][@stdlib/constants/time]: time constants.
- [`uint16`][@stdlib/constants/uint16]: 16-bit unsigned integer mathematical constants.
- [`uint32`][@stdlib/constants/uint32]: 32-bit unsigned integer mathematical constants.
- [`uint8`][@stdlib/constants/uint8]: 8-bit unsigned integer mathematical constants.
- [`unicode`][@stdlib/constants/unicode]: standard library string unicode constants.
## Examples
```javascript
var objectKeys = require( '@stdlib/utils/keys' );
var constants = require( '@stdlib/constants' );
var out = constants.float64.PI;
// returns ~3.142
out = constants.array.MAX_ARRAY_LENGTH;
// returns 4294967295
out = constants.time.HOURS_IN_DAY;
// returns 24
```
* * *
## Notice
This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].
#### Community
[![Chat][chat-image]][chat-url]
---
## License
See [LICENSE][stdlib-license].
## Copyright
Copyright © 2016-2021. The Stdlib [Authors][stdlib-authors].
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[stdlib]: https://github.com/stdlib-js/stdlib
[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/constants/main/LICENSE
[@stdlib/constants/array]: https://www.npmjs.com/package/@stdlib/constants/tree/main/array
[@stdlib/constants/complex128]: https://www.npmjs.com/package/@stdlib/constants/tree/main/complex128
[@stdlib/constants/complex64]: https://www.npmjs.com/package/@stdlib/constants/tree/main/complex64
[@stdlib/constants/float16]: https://www.npmjs.com/package/@stdlib/constants/tree/main/float16
[@stdlib/constants/float32]: https://www.npmjs.com/package/@stdlib/constants/tree/main/float32
[@stdlib/constants/float64]: https://www.npmjs.com/package/@stdlib/constants/tree/main/float64
[@stdlib/constants/int16]: https://www.npmjs.com/package/@stdlib/constants/tree/main/int16
[@stdlib/constants/int32]: https://www.npmjs.com/package/@stdlib/constants/tree/main/int32
[@stdlib/constants/int8]: https://www.npmjs.com/package/@stdlib/constants/tree/main/int8
[@stdlib/constants/path]: https://www.npmjs.com/package/@stdlib/constants/tree/main/path
[@stdlib/constants/time]: https://www.npmjs.com/package/@stdlib/constants/tree/main/time
[@stdlib/constants/uint16]: https://www.npmjs.com/package/@stdlib/constants/tree/main/uint16
[@stdlib/constants/uint32]: https://www.npmjs.com/package/@stdlib/constants/tree/main/uint32
[@stdlib/constants/uint8]: https://www.npmjs.com/package/@stdlib/constants/tree/main/uint8
[@stdlib/constants/unicode]: https://www.npmjs.com/package/@stdlib/constants/tree/main/unicode