Javascript Number toTimeCode()

Number.prototype.toTimeCode = function(){
 var minutes = Math.floor(this/60);
 var seconds = this%60;
 
 if(minutes != NaN){
  if(minutes !=0){
   return minutes + ":" + seconds;
  }//from www .  j  av  a 2  s  . co  m
  else{
   return seconds;
  }
 }
 else{
  return NaN;
 }
};