@stdlib/assert-is-leap-year

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isLeapYear

Test if a value corresponds to a leap year in the Gregorian calendar.

A 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.

Installation

npm install @stdlib/assert-is-leap-year

Usage

var isLeapYear = require( '@stdlib/assert-is-leap-year' );

isLeapYear( [value] )

Tests if a value corresponds to a leap year in the Gregorian calendar.

var bool = isLeapYear();
// returns <boolean>

bool = isLeapYear( new Date() );
// returns <boolean>

bool = isLeapYear( 2000 );
// returns true

bool = isLeapYear( 2017 );
// returns false

Notes

• If not provided any arguments, the function returns a boolean indicating if the current year (according to local time) is a leap year.

• If provided a value which is neither an integer value nor a Date, the function always returns false.

  var bool = isLeapYear( '2016' );
  // returns false
  
  bool = isLeapYear( null );
  // returns false

Examples

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' );
}

See Also

• @stdlib/assert-is-leap-year-cli: CLI package for use as a command-line utility.

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For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

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License

See LICENSE.

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