SMART datagrid v.1 > Classes > GridBase
It returns the number of Grid Rows. If the grid is being filtered or the row is being grouped, this number can be different from rowCount of DataSet being connected to the grid. And, if Group Row is being collapsed, the hidden child rows will not be included.
$('#calcSum').click(function () {
var sum = 0;
for (var i = 0, cnt = grid.rowCount(); i < cnt; i++) {
var row = grid.getRow(i);
if (row.isChecked()) {
sum += row.getData('salary');
}
}
$('#sum')val(sum);
});