Want to Learn Javascript

Here is the sample code for JavaScript validation against ASP dropdownlist. Script will be:

function validateDropDown(obj){
        if(document.getElementById(obj).value=='')
        {
            alert('please select an item value under any group name.'); 
            return false;
        }
    }

In code behing, you have to attach the above JavaScript function with DropDownList control and a Button control that will submit the form data to the server

protected void Page_Load(object sender, EventArgs e)
{

    DropDownList1.Attributes.Add("onchange", "javascript:return validateDropDown('" + DropDownList1.ClientID + "');");

    Button1.Attributes.Add("onclick", "javascript:return validateDropDown('" + DropDownList1.ClientID + "');");
}

You can read by following links :

http://www.w3schools.com/js/js_whereto.asp

http://www.java2s.com/Tutorial/JavaScript/CatalogJavaScript.htm

http://www.dynamicdrive.com/

go visit
http://www.w3schools.com/jsref/
to learn the basics. good luck. :)

http://w3schools.com/js/default.asp[^]