javascriptで日付時刻表示用関数

javascriptで日付時刻表示．

function dateTime(time) {
  var date = new Date();
  var year = date.getYear();
  var month = date.getMonth() + 1;
  var day = date.getDate();
  if (year < 2000) { year += 1900; }
  if (month < 10) { month = "0" + month; }
  if (day < 10) { day = "0" + day; }
  if (hour < 10) { hour = "0" + hour; }
  if (min < 10) { min = "0" + min; }
  if (sec < 10) { sec = "0" + sec; }
  var hour = date.getHours();
  var min = date.getMinutes();
  var sec = date.getSeconds();
  var msec = date.getMilliseconds();
  return year + "/" + month + "/" + day + "/"
              + hour + ":" + min + ":" + sec + "." + msec;
}

作ってみたものの，他にもnew Date()でもいけるし， Date - JavaScript | MDN にも日付文字列表示用関数の例が載ってました．