leap-day.js:给定的日期是否是leap日？

给定的日期是否是leap日？ var leapDay = require ( 'leap-day' ) typeof leapDay // => 'function' leapDay ( new Date ( 2016 , 1 , 29 ) ) // => true leapDay ( new Date ( 2016 , 1 , 28 ) ) // => false leapDay ( new Date ( 2015 , 1 , 29 ) ) // => false