function(node1, node2) {
        return node1[node1.persistenceProperty].index - node2[node2.persistenceProperty].index;
    }
function(node1, node2) {
        return node1[node1.persistenceProperty].index - node2[node2.persistenceProperty].index;
    }
function ( node1 , node2 ) { return node1 [ node1 . persistenceProperty ] . index - node2 [ node2 . persistenceProperty ] . index ; }
Sorter function for sorting records in index order
@private
@param {Ext.data.NodeInterface} node1
@param {Ext.data.NodeInterface} node2
@return {Number}
Sorter function for sorting records in index order