Help... How to get the variable from another function to other function by using parameters... thanks...

Help... How to get the variable from another function to other function by using parameters... thanks...

This is the code 

format_time = function( song_duration   ){
      var song_duration = ('0'+Math.floor(song.duration/60)%60).slice(-2)+':'+(Math.floor('0' + song.duration % 60));
}
//Update time line
update_timeline = function( song_duration   ){
$timeline.html('00:00' + "-" + song_duration);
}
update_timeline();

the result undifined??? can anyone help on this... i have problems interms of parameters... thanks...