Javascript fuzzy time (e.g '10 minutes ago') that's in exact seconds

I'm making a javascript counter that counts 'seconds ago'. I have my time in a JS time object, and I found a "time difference" function snippet here on stack overflow, but it displays "2 hours ago". How can I get it to display "5 hours, 10 minutes and 37 seconds ago."

Here's what I'm working with:

This function converts the current time and the timestamp of something into "20 seconds ago" instead of a cryptic date:

function timeDifference(current, previous) {
    var msPerMinute = 60 * 1000;
    var msPerHour = msPerMinute * 60;
    var msPerDay = msPerHour * 24;
    var msPerMonth = msPerDay * 30;
    var msPerYear = msPerDay * 365;

    var elapsed = current - previous;

    if (elapsed < msPerMinute) {
         return Math.round(elapsed/1000) + ' seconds ago';   
    } else if (elapsed < msPerHour) {
         return Math.round(elapsed/msPerMinute) + ' minutes ago';   
    } else if (elapsed < msPerDay ) {
         return Math.round(elapsed/msPerHour ) + ' hours ago';   
    } else if (elapsed < msPerMonth) {
         return 'approximately ' + Math.round(elapsed/msPerDay) + ' days ago';   
    } else if (elapsed < msPerYear) {
         return 'approximately ' + Math.round(elapsed/msPerMonth) + ' months ago';   
    } else {
         return 'approximately ' + Math.round(elapsed/msPerYear ) + ' years ago';   
    }
}

And here's what I'm using to "count up" the time each second. I'd like it to say "5 hours, 3 minutes, 10 seconds ago" and then 1 second later, "5 hours, 3 minutes, 11 seconds ago"

var newTime = new Date(data.popular[i].timestamp*1000)
var relTime = timeDifference(new Date(),newTime)

setInterval(function(){
    var theTimeEl = $('.timestamp-large').filter(function(){
        return $(this).html() == relTime
    });
    newTime.setSeconds(newTime.getSeconds() + 1);
    var relTime = timeDifference(new Date(), newTime);
    $(theTimeEl).html(relTime);
    console.log(relTime)
}, 1000)

The variable newTime is the time in the UTC javascript date format. relTime is that in "seconds ago" format. The interval loops through a bunch of timestamp elements and picks the right one for each time stamp. Then it adds a second to the time, converts it back into "fuzzy time" (seconds ago), replaces the html with the new time and logs it in the console.

How do I change "5 hours ago" to "5 hours, 37 mintues, 10 seconds ago"? The time difference function needs to be modified.