easyui datagrid生成序號列formatter

var opts1;
$('#datagrid_1').datagrid({
    columns: [
        [{
                field: 'myNo',
                title: '序號',
                align: 'center',
                width: 100,
                formatter: function (value, row, index) {
                    if (!opts1) {
                        opts1 = $('#datagrid_1').datagrid('options');
                    }
                    return opts1.pageSize * (opts1.pageNumber - 1) + index + 1;
                }
            }
        ]
    ]
});