<span style="font-size:18px;">Date.prototype.format = function (mask) 
{ 
var d = this; 
var zeroize = function (value, length) 
{ 
if (!length) length = 2; 
value = String(value); 
for (var i = 0, zeros = ''; i < (length - value.length); i++) 
{ 
zeros += '0'; 
} 
return zeros + value; 
}; 
return mask.replace(/"[^"]*"|'[^']*'|\b(?:d{1,4}|m{1,4}|yy(?:yy)?|([hHMstT])\1?|[lLZ])\b/g, function ($0) 
{ 
switch ($0) 
{ 
case 'd': return d.getDate(); 
case 'dd': return zeroize(d.getDate()); 
case 'ddd': return ['Sun', 'Mon', 'Tue', 'Wed', 'Thr', 'Fri', 'Sat'][d.getDay()]; 
case 'dddd': return ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'][d.getDay()]; 
case 'M': return d.getMonth() + 1; 
case 'MM': return zeroize(d.getMonth() + 1); 
case 'MMM': return ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'][d.getMonth()]; 
case 'MMMM': return ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'][d.getMonth()]; 
case 'yy': return String(d.getFullYear()).substr(2); 
case 'yyyy': return d.getFullYear(); 
case 'h': return d.getHours() % 12 || 12; 
case 'hh': return zeroize(d.getHours() % 12 || 12); 
case 'H': return d.getHours(); 
case 'HH': return zeroize(d.getHours()); 
case 'm': return d.getMinutes(); 
case 'mm': return zeroize(d.getMinutes()); 
case 's': return d.getSeconds(); 
case 'ss': return zeroize(d.getSeconds()); 
case 'l': return zeroize(d.getMilliseconds(), 3); 
case 'L': var m = d.getMilliseconds(); 
if (m > 99) m = Math.round(m / 10); 
return zeroize(m); 
case 'tt': return d.getHours() < 12 ? 'am' : 'pm'; 
case 'TT': return d.getHours() < 12 ? 'AM' : 'PM'; 
case 'Z': return d.toUTCString().match(/[A-Z]+$/); 
// Return quoted strings with the surrounding quotes removed 
default: return $0.substr(1, $0.length - 2); 
} 
}); 
};</span> 

Date.prototype.format =function(format)
{
var o = {
"M+" : this.getMonth()+1, //month
"d+" : this.getDate(), //day
"h+" : this.getHours(), //hour
"m+" : this.getMinutes(), //minute
"s+" : this.getSeconds(), //second
"q+" : Math.floor((this.getMonth()+3)/3), //quarter
"S" : this.getMilliseconds() //millisecond
}
if(/(y+)/.test(format)) format=format.replace(RegExp.$1,
(this.getFullYear()+"").substr(4- RegExp.$1.length));
for(var k in o)if(new RegExp("("+ k +")").test(format))
format = format.replace(RegExp.$1,
RegExp.$1.length==1? o[k] :
("00"+ o[k]).substr((""+ o[k]).length));
return format;
}
var date = new Date(parseInt("1347497754133"));
date.format("yyyy-MM-dd");