strftime.js (strftime github) is one of the best time formatting libraries. It's extremely light - 30KB - and effective. Using it you can convert seconds into time easily in one line of code, relying mostly on the native Date class.
When creating a new Date, each optional argument is positional as follows:
new Date(year, month, day, hours, minutes, seconds, milliseconds);
So if you initialize a new Date with all arguments as zero up to the seconds, you'll get:
var seconds = 150;
var date = new Date(0,0,0,0,0,seconds);
=> Sun Dec 31 1899 00:02:30 GMT-0500 (EST)
You can see that 150 seconds is 2-minutes and 30-seconds, as seen in the date created. Then using an strftime format ("%M:%S" for "MM:SS"), it will output your minutes' string.
var mm_ss_str = strftime("%M:%S", date);
=> "02:30"
In one line, it would look like:
var mm_ss_str = strftime('%M:%S', new Date(0,0,0,0,0,seconds));
=> "02:30"
Plus this would allow you to interchangeable support HH:MM:SS and MM:SS based on the number of seconds. For example:
# Less than an Hour (seconds < 3600)
var seconds = 2435;
strftime((seconds >= 3600 ? '%H:%M:%S' : '%M:%S'), new Date(0,0,0,0,0,seconds));
=> "40:35"
# More than an Hour (seconds >= 3600)
var seconds = 10050;
strftime((seconds >= 3600 ? '%H:%M:%S' : '%M:%S'), new Date(0,0,0,0,0,seconds));
=> "02:47:30"
And of course, you can simply pass whatever format you want to strftime if you want the time string to be more or less semantic.
var format = 'Honey, you said you\'d be read in %S seconds %M minutes ago!';
strftime(format, new Date(0,0,0,0,0,1210));
=> "Honey, you said you'd be read in 10 seconds 20 minutes ago!"