jqGrid在搜索中仅显示"IsNull“和"Is Not Null”选项

$("#grid").jqGrid({
    url: "data.json",
    datatype: "json",
    colModel: [
        { name: "id", label: "ID", width: 50 },
        { name: "name", label: "Name", width: 100 },
        { name: "age", label: "Age", width: 50 }
    ],
    search: true,
    postData: {
        filters: {
            groupOp: "AND",
            rules: [
                { field: "name", op: "nu" }, // IsNull
                { field: "age", op: "nn" } // Is Not Null
            ]
        }
    },
    jsonReader: {
        root: "rows",
        page: "page",
        total: "total",
        records: "records",
        repeatitems: false
    },
    pager: "#pager",
    rowNum: 10,
    rowList: [10, 20, 30],
    sortname: "id",
    sortorder: "asc",
    viewrecords: true,
    caption: "jqGrid Example"
});