time ago in vanilla js

function timeSince(timeStamp) {
    var now = new Date(),
        secondsPast = (now.getTime() - timeStamp.getTime()) / 1000;
    if(secondsPast < 60){
        return parseInt(secondsPast) + 's';
    }
    if(secondsPast < 3600){
        return parseInt(secondsPast/60) + 'm';
    }
    if(secondsPast <= 86400){
        return parseInt(secondsPast/3600) + 'h';
    }
    if(secondsPast > 86400){
        day = timeStamp.getDate();
        month = timeStamp.toDateString().match(/ [a-zA-Z]*/)[0].replace(" ","");
        year = timeStamp.getFullYear() == now.getFullYear() ? "" :  " "+timeStamp.getFullYear();
        return day + " " + month + year;
    }
}