jQuery.get method : trying to understand source code

jQuery.get method : trying to understand source code

  
    
   
  1.   get: function( url, data, callback, type ) {
    2. 
   
  2.  // shift arguments if data argument was omited
    3. 
   
  3.  if ( jQuery.isFunction( data ) ) {
    4. 
   
  4.  type = type || callback;
    5. 
   
  5.  callback = data;
    6. 
   
  6.  data = null;
    7. 
   
  7.  }
    8. 
   
  8.  return jQuery.ajax({
    9. 
   
  9.  type: "GET",
    10. 
   
  10.  url: url,
    11. 
   
  11.  data: data,
    12. 
   
  12.  success: callback,
    13. 
   
  13.  dataType: type
    14. 
   
  14.  });
    15. 
   
  15. },
    16. 
  

  

   Above is the jQuery.get method from ajax.js . I was wondering why the 4th line is 
  

  

   

  

  

   is 
  

  

   

  

  

   
     
    
      
  1.  type = type || callback;
    2. 
     

     

      

     

     

      I think that line should be 
     

     

      

     

     

      

     

     

      
        
    
         
  1.  type = callback;
    2. 
        

        

         

        

        

         The way I see it, if data is function then type *must* be nil . If type has a value
        

        

         then one parameter before type must have been dropped.
        

        

         

        

        

         Am I missing something here?