firstAscending

Sets whether the first click over the header cell with sort the column ascending or descending. The default value is true:

$("#grid").shieldGrid({
    dataSource: {
        data: [
            { ID: 1, name: "name1" },
            { ID: 2, name: "name2" }
        ]
    },
    sorting: {
        multiple: true,
        allowUnsort : true,
        firstAscending: false
    },
    columns: [
        { field: "ID", title: "Unique Number", format: "{0:c}" },
        { field: "name", title : "Name", width: “300px }
    ]
});