Time Difference

time-difference

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 'less than a minute ago';   
    }

    else if (elapsed < msPerHour) {
        if( Math.round(elapsed/msPerMinute) === 1 ) {
            return '1 minute ago';
        } else {
            return Math.round(elapsed/msPerMinute) + ' minutes ago'; 
        }
    }

    else if (elapsed < msPerDay ) {
        if( Math.round(elapsed/msPerHour) === 1 ) {
            return '1 hour ago';
        } else {
            return Math.round(elapsed/msPerHour ) + ' hours ago';
        }           
    }

    else if (elapsed < msPerMonth) {
        if( Math.round(elapsed/msPerDay) === 1 ) {
            return '1 day ago';
        } else {
            return Math.round(elapsed/msPerDay) + ' days ago';
        }           
    }

    else if (elapsed < msPerYear) {
        if( Math.round(elapsed/msPerMonth) === 1 ) {
            return '1 month ago'; 
        } else {
            return Math.round(elapsed/msPerMonth) + ' months ago';
        }           
    }

    else {
        if( Math.round(elapsed/msPerYear) === 1 ) {
            return '1 year ago'; 
        } else {
            return Math.round(elapsed/msPerYear ) + ' years ago'; 
        }          
    }
};