Check if a given year is leap year. #learnjs

gistfile1.js

/**
 * #learnjs
 * Check if a given year is leap year.
 * @param {int} [year] Year to be evaluated. If no date is used defines the client year.
 * @return {boolean} Returns <em>true</em> is year a leap year, otherwise <em>false</em>.
 */
function isLeapYear (year) {
  return (new Date(year || (new Date).getFullYear(), 1, 29, 0, 0).getMonth() != 2);
}