あ〜すでに忘れていた！

javascript 教えてgoo

javaで日付
http://oshiete.goo.ne.jp/qa/7704358.html

日付文字列の変換。一昨日のことなのに。

&#65279;<!DOCTYPE html>
<title></title>
<meta charset="UTF-8">

<body>
<h1>叩かれ台</h1>
<form action="#" id="test">
  <p>
    <input type="text" name="target" value="">
    <input type="button" value="+" onclick="hoge('+')">
    <input type="button" value="*" onclick="hoge('*')">
    <input type="button" value="-" onclick="hoge('-')">
  </p>
</form>

<script>
var ERR_MESS = '不正です';
var TARGET = document.getElementById ('test').elements['target'];

function hoge (cmnd) {
  var value = TARGET.value;
  var result = null;
  var dateObj = null;
  
  switch (cmnd) {
  case '*' :
    result = toDateStr (addDay (new Date, 0));
    break;

  case '-' :
    dateObj = dateCheck (value);
    if (! dateObj) {
      alert (ERR_MESS);
      return;
    }
    result = toDateStr (addDay (dateObj, -1));
    break;
    
  case '+' :
    dateObj = dateCheck (value);
    if (! dateObj) {
      alert (ERR_MESS);
      return;
    }
    result = toDateStr (addDay (dateObj, 1));
    break;
  }
  TARGET.value = result;
}


function addDay (dateObject, offsetDay) {
  var day = dateObject.getDate ();
  dateObject.setDate (day + offsetDay);
  return dateObject;
}


function toDateStr (dateObject) {
  var d = dateObject;
  return [
    padding (d.getFullYear (), 4),
    padding (d.getMonth () + 1, 2),
    padding (d.getDate (), 2),
    '00'
  ].join ('');
}

function padding (num, z) {
  return ((Array (z)).join ('0') + String (num)).slice (-z);
}


function dateCheck (str) {
  var ymdx = str.match (/^(\d{4})(\d{2})(\d{2})(\d{2})$/);
  var result = null;

  if (ymdx) {
    result = new Date (Number (ymdx[1]), Number (ymdx[2]) - 1, Number (ymdx[3]));
  }
  
  return result;
}
</script>