how to set values to combobox dynamically in javascript

Question

this is how i set value to a combobox using dwr call,

var reportID = '<%=reportid%>'; var reportName = '<%=reportname%>'; loadReportNames(reportUserID);

function loadReportNames(reportUserID){
    CustomiseReportAction.getReportNames(reportUserID, addReportNamesDropDown);
}
function addReportNamesDropDown(resultMap){
    dwr.util.removeAllOptions("reportnames");
    dwr.util.addOptions("reportnames",resultMap);
}

after loading the combo box i set values to loaded combo like this,

document.getElementById("reportnames").value=reportID;

but the reportID is not set,

what could be the problem please help me to resolve this.

UPDATE :

function addCombo() {
    var reportID = '<%=reportid%>';
    var reportName = '<%=reportname%>';
    var textb = document.getElementById("reportnames");

    var option = document.createElement("option");
    option.text = reportName;
    option.value = reportID;
    option.selected="selected";
    try {
        textb.add(option, null); //Standard
    }catch(error) {
        textb.add(option); // IE only
    }
    textb.value = "";
}

used above method it gives me no exception but no results.

Regards

Answer 1

I have not removed the value rather i added the following code, it solved me the problem.

function addCombo() {
    var reportID = '<%=reportid%>';
    var options= document.getElementById('reportnames').options;
    for (var i= 0, n= options.length; i < n ; i++) {
        if (options[i].value==reportID) {
            document.getElementById("reportnames").selectedIndex = i;
            break;
        }
    }
}