Paging in REST

I am trying to implement paging in REST, below is my main main function:

var _lim =  Utilities.ListItemManager(“Announcements”); 

function _readListItemsPaged() {  
        var dfd = $.Deferred(); 
        var itemsPromise = _lim.readAllItems(3);    //passing the number of items per page
        itemsPromise.then(    
         function (data, status, jqXHR) {     
            _onReadItemsPagedSucceed(data);   
              dfd.resolve();           
         },
         function (jqXHR, status, error) {   
             Utilities.LogResult(error);     
             dfd.reject();          
         });

         return dfd.promise();     
}

the _lim looks like this, with the readAllItems

Utilities.ListItemManager = function (listName){ 

var initialSize = 0;

var skip; 

function _readAllItems(pageSize) {
     var baseUrl = SP.Utilities.UrlBuilder.urlCombine(_spPageContextInfo.webServerRelativeUrl, "_api/web/lists/getByTitle('" + listName + "')/items");   
     skip = initialSize * pageSize;   
     baseUrl = encodeURI(baseUrl) + "?$skiptoken=Paged%3dTRUEp_ID%3d" + skip + "&$top=" + pageSize;
     initialSize++;    
     var dfd = $.ajax({        
          url: baseUrl,         
          type: "GET",         
          contentType: "application/json;odata=verbose",         
          headers: {             
                "accept": "application/json;odata=verbose"         
           }
      });     
      return dfd; 
} 
  var publicMembers = {    
        readAllItems: _readAllItems 
}

 return publicMembers;
}

But when I click the button that calls the _lim.readAllItems(3), everytime the initialSize becomes 0 again.