I need to make Date format from string javascript

You can use Date function

var d = new Date("15 Feb, 2016");
alert(d.getFullYear()+","+(d.getMonth()+1)+"," + d.getDate());

You could look at a library like Moment to make this easier. Then this code will format it how you want:

var myDate = "15 Feb, 2016";
moment(myDate, "DD MMM, YYYY").format("YYYY,MM,DD")

You can see in another answer how to do it with pure javascript, but Moment will save you some work and also make it quite easy to change your final format if you decide you want something different later.

You could create a date instance and then use it like this...

var date = new Date('15 Feb, 2016');
var dateString = date.getFullYear() + ', ' + (date.getMonth() + 1) + ', ' + date.getDate();

There are also libraries that could help with other formats:

MomentJS date.format

you first need to parse this string into a Date object

var strDate = "15 Feb, 2016";
var months = [ "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" ];
var dateFields = strDate.split( " " ).map( function(value){ if ( value.indexOf( "," ) != -1){ return value.substring(0, value.length - 1); } return value; } );
var date = new Date();
date.setDate(dateFields[0]);
date.setMonth(months.indexOf(dateFields[1]));
date.setFullYear( dateFields[2] );

Now you can display it in whichever format you want

alert( date.getFullYear() + "," + (date.getMonth() + 1) + "," + date.getDate() );

This only gives the value in single digit if they are in single digit, so use this method for padding

function pad(var value) {
    if(value < 10) {
        return '0' + value;
    } else {
        return value;
    }
}
alert( date.getFullYear() + "," + pad(date.getMonth() + 1) + "," + pad(date.getDate()) );

While you do need to parse the string, there's no need to create a Date object. All you need to do is get the parts, map the month name to a number and write a formatted string.

The parsing part is the same as parsing it for a Date, but formatting the output string is much simpler:

// Reformat date string like d mmm, y to y, m, d
function reformatDateString(s) {
  var months = {jan:'01',feb:'02',mar:'03',apr:'04',may:'05',jun:'06',
                jul:'07',aug:'08',sep:'09',oct:'10',nov:'11',dec:'12'};
  var b = s.match(/\w+/g);
  return b && b[2] + ',' + months[b[1].toLowerCase()] + ',' + b[0];
}

document.write(reformatDateString('15 Feb, 2016'));