@stdlib/assert-is-leap-year

<details> <summary> About stdlib... </summary> <p>We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.</p> <p>The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.</p> <p>When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.</p> <p>To join us in bringing numerical computing to the web, get started by checking us out on <a href="https://github.com/stdlib-js/stdlib">GitHub</a>, and please consider <a href="https://opencollective.com/stdlib">financially supporting stdlib</a>. We greatly appreciate your continued support!</p> </details> # isLeapYear [![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]  > Test if a value corresponds to a [leap year][leap-year] in the [Gregorian calendar][gregorian-calendar]. A [leap year][leap-year] is defined as any year which is exactly divisible by `4`, except for years which are exactly divisible by `100` and not by `400`. In this definition, `100` corresponds to years marking a new century, and `400` corresponds to the length of the _leap cycle_. <section class="installation"> ## Installation ```bash npm install @stdlib/assert-is-leap-year ``` </section> <section class="usage"> ## Usage ```javascript var isLeapYear = require( '@stdlib/assert-is-leap-year' ); ``` #### isLeapYear( \[value] ) Tests if a `value` corresponds to a [leap year][leap-year] in the [Gregorian calendar][gregorian-calendar]. ```javascript var bool = isLeapYear(); // returns <boolean> bool = isLeapYear( new Date() ); // returns <boolean> bool = isLeapYear( 2000 ); // returns true bool = isLeapYear( 2017 ); // returns false ``` </section>  <section class="notes"> ## Notes - If not provided any `arguments`, the function returns a `boolean` indicating if the current year (according to local time) is a [leap year][leap-year]. - If provided a `value` which is neither an integer value nor a [`Date`][date-object], the function **always** returns `false`. ```javascript var bool = isLeapYear( '2016' ); // returns false bool = isLeapYear( null ); // returns false ``` </section>  <section class="examples"> ## Examples  ```javascript var isLeapYear = require( '@stdlib/assert-is-leap-year' ); var bool; var i; for ( i = 0; i < 2021; i++ ) { bool = isLeapYear( i ); console.log( 'The year %d %s a leap year.', i, ( bool ) ? 'is' : 'is not' ); } ``` </section>   <section class="related"> ## See Also - <span class="package-name">[`@stdlib/assert-is-leap-year-cli`][@stdlib/assert-is-leap-year-cli]</span><span class="delimiter">: </span><span class="description">CLI package for use as a command-line utility.</span> </section>   <section class="main-repo" > * * * ## 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 © 2016-2024. The Stdlib [Authors][stdlib-authors]. </section>   <section class="links"> [@stdlib/assert-is-leap-year-cli]: https://www.npmjs.com/package/@stdlib/assert-is-leap-year-cli [npm-image]: http://img.shields.io/npm/v/@stdlib/assert-is-leap-year.svg [npm-url]: https://npmjs.org/package/@stdlib/assert-is-leap-year [test-image]: https://github.com/stdlib-js/assert-is-leap-year/actions/workflows/test.yml/badge.svg?branch=v0.2.2 [test-url]: https://github.com/stdlib-js/assert-is-leap-year/actions/workflows/test.yml?query=branch:v0.2.2 [coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/assert-is-leap-year/main.svg [coverage-url]: https://codecov.io/github/stdlib-js/assert-is-leap-year?branch=main  [chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg [chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im [stdlib]: https://github.com/stdlib-js/stdlib [stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors [cli-section]: https://github.com/stdlib-js/assert-is-leap-year#cli [cli-url]: https://github.com/stdlib-js/assert-is-leap-year/tree/cli [@stdlib/assert-is-leap-year]: https://github.com/stdlib-js/assert-is-leap-year/tree/main [umd]: https://github.com/umdjs/umd [es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules [deno-url]: https://github.com/stdlib-js/assert-is-leap-year/tree/deno [deno-readme]: https://github.com/stdlib-js/assert-is-leap-year/blob/deno/README.md [umd-url]: https://github.com/stdlib-js/assert-is-leap-year/tree/umd [umd-readme]: https://github.com/stdlib-js/assert-is-leap-year/blob/umd/README.md [esm-url]: https://github.com/stdlib-js/assert-is-leap-year/tree/esm [esm-readme]: https://github.com/stdlib-js/assert-is-leap-year/blob/esm/README.md [branches-url]: https://github.com/stdlib-js/assert-is-leap-year/blob/main/branches.md [stdlib-license]: https://raw.githubusercontent.com/stdlib-js/assert-is-leap-year/main/LICENSE [leap-year]: https://en.wikipedia.org/wiki/Leap_year [gregorian-calendar]: https://en.wikipedia.org/wiki/Gregorian_calendar [date-object]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date [standard-streams]: https://en.wikipedia.org/wiki/Standard_streams [mdn-regexp]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions </section>