javascript - IndexOf not Supported in IE8 Browser

I have cascaded dropdown in my application, cascaded using jquery, now my problem is it is working smoothly with IE9, Firefox, Opera and Safari but does not work with any of browsers like IE7,IE8 etc.

I surfed for the problem and found that error is due to indexOf in my jquery code, i tried it by removing indexOf but still it is giving the same error..

Note: Is there any work around in telerik script to remove indexOf, coz new only i can find indexOf in their script.

Below is the Code:

function OnClientSelectedIndexChanged(sender, eventArgs) {
var senderId = sender.get_id().toString();


var uniqueName = senderId.substring(senderId.lastIndexOf('_'), senderId.length);

if(senderId.indexOf("drpdwnCondition") > 0)
{
   return false;
}

var selectedItem = eventArgs.get_item();
var selectedValue = selectedItem.get_value().split('_');

$.ajax({ type: "POST", async: true,
    url: "/SalesRepresentativeMonitoring.aspx/GetData", contentType: "application/json; charset=utf-8",
    data: "{value:" + JSON.stringify(selectedValue[1]) + "}", dataType: "json",
    success: function (msg) {
        var resultAsJson = msg.d // your return result is JS array
        // Now you can loop over the array to get each object
        var cnditionCombo = $find("ctl00_ContentPlaceHolder1_radDock_C_Filter_drpdwnCondition" + uniqueName.toString());
        cnditionCombo.clearSelection();
        cnditionCombo.trackChanges();
        cnditionCombo.clearItems();

        for (var i in resultAsJson) {
            //alert(resultAsJson[i]);
            var item = new Telerik.Web.UI.RadComboBoxItem();
            item.set_text(resultAsJson[i]);
            item.set_value(resultAsJson[i]);
            cnditionCombo.get_items().add(item);
        }
        var itemAtIndex = cnditionCombo.get_items().getItem(0);  //get item in detailCB
        itemAtIndex.select();
        cnditionCombo.commitChanges();

    }
});

}

Thanking you..

Answer

The indexOf() method of Arrays is not implemented in IE < 9. As you're using jQuery you can make use of the $.inArray(), e.g.

var arr = ["foo", "bar", "baz"],
    bazIndex = $.inArray("baz", arr), // 2
    doesntExistIndex = $.inArray("notThere", arr); // -1

Here's the documentation: http://api.jquery.com/jQuery.inArray/.