Get selected item in CRM grid

The following snippet will allow you to retrieve an array containing the Id values of the selected records in the grid:

    //    get array of selected records
    var a = document.all['crmGrid'].InnerGrid.SelectedRecords;
    var selectedItems = new Array(a.length);
    for (var i=0; i < a.length; i++)
    {
        selectedItems[i] = a[i][0];
    }
    alert(selectedItems);

To get all of the records in the grid (ie. “All Records on Current Page”):

    //    array of all records on current page
    var iTotal = document.all['crmGrid'].InnerGrid.NumberOfRecords;
    var o = document.all['crmGrid'].InnerGrid;
    var allItems = new Array;
    var ii = 0;
    for (var i=0; i < iTotal; i++)
    {
        allItems[ii] = o.rows[i].oid;
        ii++;
    }
    alert(allItems);

The source: http://blog.customereffective.com/blog/2009/02/javascript-snippets-for-working-with-grids-in-crm.html