jquery EasyUI的formatter格式化

$('#tt').datagrid({
    title:'Formatting Columns',
    width:550,
    ">250,
    url:'datagrid_data.json',
    columns:[[
        {field:'itemid',title:'Item ID',width:80},
        {field:'productid',title:'Product ID',width:80},
        {field:'listprice',title:'List Price',width:80,align:'right',
            formatter:function(val,rec){
                if (val < 20){
                    return '<span style="color:red;">('+val+')</span>';
                } else {
                    return val;
                }
            }
        },
        {field:'unitcost',title:'Unit Cost',width:80,align:'right'},
        {field:'attr1',title:'Attribute',width:100},
        {field:'status',title:'Status',width:60}
    ]]
});