Looping through Radgrid in JS is slow, can this be faster? I do a single select in one radgrid, and based upon that selection I want to select multiple rows in a different radgrid:

&lt;telerik:RadGrid ID="rgPaymentLines"&gt; &lt;ClientEvents OnRowSelected="RowPaymentSelected"/&gt; ... &lt;/telerik:RadGrid&gt;

&lt;telerik:RadCodeBlock ID="RadCodeBlock1" runat="server"&gt;
    &lt;script type="text/javascript"&gt;

        function RowPaymentSelected(sender, eventArgs) {
            var grid = $find("&lt;%=rgPaymentLines.ClientID %&gt;");
            var MasterTablePayment = grid.get_masterTableView();
            var paymentRow = MasterTablePayment.get_selectedItems()[0];
            var paymentCell = MasterTablePayment.getCellByColumnUniqueName(paymentRow, "DossierID")
            selectDossierRow(paymentCell.innerHTML);
        }
        function selectDossierRow(dossierID) {
            var gridDossier = $find("&lt;%=rgDossiersAdmin.ClientID %&gt;");
            var MasterTableDossier = gridDossier.get_masterTableView();
            var rows = MasterTableDossier.get_dataItems();

            MasterTableDossier.clearSelectedItems();
            for (var i = 0; i &lt; rows.length; i++) {
                if (MasterTableDossier.getCellByColumnUniqueName(rows[i], "columnDossierID").innerHTML == dossierID) {
                    MasterTableDossier.selectItem(i);
                }
            }
        }
welcome to Code Review and thank you for your question. You need to profile the code to see for yourself where it is slow. Firebug and Chrome can do this. Only then will you be able to optimize your code.

Side note: Be careful about variable names, some of them seem to be in French (dossier).