Add hour and minutes to a string with hh:mm?

I have a string containing 13:00 , i have an duration of 90 for example and i have to convert the duration to hh:mm which i made it. Now i have a string with 1:30. How can i add this 1:30 string to the other 13:00 string so i can compare it with another strings? This is how i conver the duration

var bookH = Math.floor(data[0]['Duration'] / 60);
    var bookM = data[0]['Duration'] % 60;
    var bookingDurationToHour = bookH + ':' + bookM;

There is momentjs in the project but i still do not know how can i do that.