code: function peekNextJob(){
    if(queue.size() <= 0)
      return null;
  
    let job = null;
  
    do{
      job = map[queue.peek().id];
      if(!job) queue.pop();
    }while(!job && queue.size() > 0);
  
    return (!!job)?job:null;
  }
docs: Return, but not remove the next valid job
  @return Next valid job