我有这个功能：

var rowCellClass = function (row, columnfield, value, rowData) {
    if (rowData.ConfirmDate != null && rowData.ConfirmDate != '') {
        return 'green';
    }
}

这个网格：

var gridPreDocWar = function (data) {
    var gridDataPreDocWar = generateConfirmations(1);
    var source ={
        totalrecords: gridDataPreDocWar.length,
        localData: gridDataPreDocWar,
        datafields:[
            { name: 'RecordId', type: 'int' },
            { name: 'ConfirmDate', type: 'date' },

        ],
        datatype: "array",
    };
    var dataAdapter = new $.jqx.dataAdapter(source);
    $("#grid").jqxGrid({
        
        theme: "ui-redmond",
        width: '100%',
        autoheight: true,
        source: dataAdapter,
        showfilterrow: true,
        filterable: true,
        selectionmode: 'multiplecellsextended',
        columns: [
            { text: 'Updated', datafield: 'ConfirmDate', columntype: 'date', filtertype: 'input', width: '10%', cellsformat: 'dd.MM.yyyy HH:mm', cellclassname: rowCellClass },
            
        ]
    });
}

我可以看到ConfirmDate不为null或空，但cellclassname函数没有改变单元格的颜色。会是什么原因呢？