get_expanded()

This property is of type Boolean and returns whether the row with the specified index is expanded. Please note that this property is meaningful, when the HierarchyLoadMode setting is set to Client.

Example:

function CheckExpandedState() {
    var masterTable = $find("<%= RadGrid1.ClientID %>").get_masterTableView();
    alert(masterTable.get_dataItems()[2].get_expanded());
}