Simple age calculation function

calcAge.js

function calcAge(YYYY,MM,DD) {

  var today = new Date(),
      todayYYYY = today.getFullYear(),
      todayMM = today.getMonth() + 1,
      todayDD = today.getDate();
  
  return (todayYYYY - YYYY) - (todayMM < MM || (todayMM == MM && todayDD < DD) ? 1 : 0);

}