Edit in JSFiddle

var now = new Date();  
var year= now.getFullYear();  
var mon = (now.getMonth()+1)>9 ? ''+(now.getMonth()+1) : '0'+(now.getMonth()+1);  
var day = now.getDate()>9 ? ''+now.getDate() : '0'+now.getDate();  

alert(year + mon + day);  
alert(year + '년 ' + mon + '월 ' + day + '일');  
alert(year + '-'+ mon+ '-' + day);