I got this problem on formating the time

This is the the function

format_time = function(seconds,minutes){

var minutes = ('0'+Math.floor(minutes/60)%60).slice(-2);

var seconds = (Math.floor('0' + seconds % 60));

return minutes + ":" + seconds;

}

format_time(song.duration)

The problem is the minutes will display aN? but the seconds display the right result..

I just realize the problem is all about the value that been returning... how can both of them to be return???