extjs store中数据转换成json

var datar = new Array();  
var jsonDataEncode = "";  
var records = store.getRange();  
for (var i = 0; i < records.length; i++) {  
    datar.push(records[i].data);  
}  
jsonDataEncode = Ext.util.JSON.encode(datar);  

Share.AjaxRequest({
                                url : ‘fen/chargefen‘,
                                params : {
                                    listdata : Ext.encode(Ext.pluck(grid.getStore().data.items, ‘data‘)),
                                    loadname : btn.up("window").loadname
                                },
                                callback : function() {
                                    btn.up("window").close();
                                }
                            });