mixedcollection and grouping

[tofsteel]

hello...

how do i do group by my mixedcollection object items. so

var myObject = Ext.util.MixedCollection(false);

myObject.add({dataSourceName : 'customer', rec : {..........}});
myObject.add({dataSourceName : 'creditCart', rec : {..........}});
myObject.add({dataSourceName : 'customer', rec : {..........}});
myObject.add({dataSourceName : 'creditCart', rec : {..........}});
myObject.add({dataSourceName : 'custProperty', rec : {..........}});
myObject.add({dataSourceName : 'customer', rec : {..........}});
myObject.add({dataSourceName : 'creditCart, rec : {..........}});
myObject.add({dataSourceName : 'customer', rec : {..........}});
vs vs vs ...............

finally grouped for dataSourceName property -->
'customer'
'creditCart'
'custProperty'

thanks for advance. . .