JavaScript-日期格式化（一）

/**
* 日期格式化，
* @param date 要格式化的日期
* @param pattern 进行格式化的模式
*     支持的模式字母有：
*     y:年,
*     M:年中的月份(1-12),
*     d:月份中的天(1-31),
*     H:小时(0-23),
*     h:小时(0-12),
*     m:分(0-59),
*     s:秒(0-59),
*     S:毫秒(0-999),
*     E:星期(以汉语表示),
*     e:星期(以英文表示),
*     A:上午/下午标识,
*     a:AM/PM标识
* @return
*/
function formatDate(date,pattern){
var d;
if((d=parseDate(date))==null){
return "";
}
if(!pattern){
pattern = "yyyy-MM-dd";
}
var arrWeek = ["星期日","星期一","星期二","星期三","星期四","星期五","星期六","Sunday","Monday","Tuesday","Tuesday","Thursday","Friday","Saturday"];
var value = new Object();
value["y"] = parseString(date.getFullYear());
value["M"] = parseString(date.getMonth() + 1);
value["d"] = parseString(date.getDate());
value["H"] = parseString(date.getHours());
value["h"] = parseString(value["H"] > 12 ? (value["H"]-12) : value["H"]);
value["m"] = parseString(date.getMinutes());
value["s"] = parseString(date.getSeconds());
value["S"] = parseString(date.getMilliseconds());
value["E"] = arrWeek[date.getDay()];
value["e"] = arrWeek[date.getDay() + 7];
value["a"] = (value["H"] > 12 ? "PM" : "AM");
value["A"] = (value["H"] > 12 ? "下午" : "上午");
var result = "";
var i = 0;
var hasE = false;//是否出现过星期
var hasAMPM = false;//是否出现过上午下午
while(i < pattern.length){
var c = pattern.charAt(i++);
var lc = c;//记录本次要处理的字母,如'y'
var tmpStr = c;//本次在处理的字母格式,如'yyyy'
while(i < pattern.length && (c=pattern.charAt(i))==lc){
tmpStr += c;
i++;
}
if(value[lc]!=""&&value[lc]!=null&&value[lc]!="undefined"){
//本次要处理的字母是模式母
if((lc == "E" || lc == "e") && !hasE){
//星期
result += value[lc];
hasE = true;
} else if(lc == "E" || lc == "e") {
result += tmpStr;
} else if((lc=="a" || lc == "A")  && !hasAMPM){
//上下午
result += value[lc];
hasAMPM = true;
} else if((lc=="a" || lc == "A") ){
result += tmpStr;
} else {
//如果是 单个的日期，月份，小时，分，秒的字符串，不能再进行字符串的截取操作
if(tmpStr == "d" || tmpStr == "M" || tmpStr=="H" || tmpStr=="h" || tmpStr == "m" || tmpStr == "s"){
result += value[lc];
} else {
result += value[lc].fillChar(tmpStr.length);
}
}
} else {//非模式字母，直接输出
result += tmpStr;
}
}
return result;
}

var date = new Date();
document.write(formatDate(date,"yyyy-MM-dd HH:mm:ss.SSS E") + "<br>");
document.write(formatDate(date,"yyyy年MM月dd日 HH时mm分ss秒 E") + "<br>");
document.write(formatDate(date,"yyyy-M-d hh:mm:ss.SSS A E") + "<br>");
document.write(formatDate(date,"MM/dd/yy hh:mm:ss a e") + "<br>");
document.write(formatDate(date,"M/d/yyyy") + "<br>");