function Test_Country_OnItemSelection(ddlCountryId, ddlcityId, DataList) {
    var ddlCountry = document.getElementById(ddlCountryId);
    var selectedValue = ddlCountry.options[ddlCountry.selectedIndex].value;
    var selectedText = ddlCountry.options[ddlCountry.selectedIndex].text;

    var ddlcity = document.getElementById(ddlcityId);
}

I have the above JavaScript function in which I'm passing parameters for dropdownlists ddlCountryId and ddlcityId. I then pass the final parameter DataList which is a C# object defined as List<City> and it contains a CityId, CityName & CountryID.

How can I convert the DataList object to a JavaScript array that I can then filter on CountryID == selectedValue and then refresh dropdownlist ddlcity after applying my filter?