日付時刻をリアルタイム表示

/**
 * 日付時刻をリアルタイム表示
 *
 * usage:
 * <div id="nowdatetime"></div> ---> e.g. <div id="nowdatetime">2013年5月18日(土) 15:08:46</div>
 *
 * @author ao-system
 */
(function(window,document){
	var weekAry = ['日','月','火','水','木','金','土'];
	draw();
	function strpad(val) {
		return (!isNaN(val) && val.toString().length == 1) ? '0' + val : val;
	}
	function draw() {
		var date = new Date();
		var year = date.getFullYear();
		var month = date.getMonth() + 1;
		var week = date.getDay();
		var day = date.getDate();
		var hour = strpad(date.getHours());
		var minute = strpad(date.getMinutes());
		var second = strpad(date.getSeconds());
		var result = year + '年 ' + month + '月' + day + '日(' + weekAry[week] + ') ' + hour + ':' + minute + ':' + second;
		document.getElementById('nowdatetime').innerHTML = result;
		setTimeout(function(){ draw(); },500);
	}
})(window,document);