Common methods for Javascript select drop-down box operations_Form special effects

function AddDropDownList(id,fatherCtl)
{
if (!document.getElementById(id))
{
var ddl = document.createElement('select');
ddl.setAttribute("id",id);
if(fatherCtl&&document.getElementById (fatherCtl))
document.getElementById(fatherCtl).appendChild(ddl);
else
document.body.appendChild(ddl);
}
}
//Delete the specified The drop-down box
function RemoveDropDownList(id)
{
var ctl = document.getElementById(id);
if(ctl)
ctl.parentNode.removeChild(ctl);
}
//Add options to the drop-down box
function AddDDDLOption(id,text,value)
{
var ctl = document.getElementById(id);
if(ctl)
{
ctl.options[ctl.options.length] = new Option(text,value);
}
}
//Remove all options
function RemoveAllDDLOptions(id)
{
var ctl = document.getElementById(id);
if(ctl)
{
ctl.options.length=0;
}
}
//Delete Options for specifying index
function RemoveDDLOption(id,index)
{
var ctl=document.getElementById(id);
if(ctl && ctl.options[index])
{
ctl.options[index]=null;
}
}
//Get the value selected in the drop-down box
function GetDDLSelectedValue(id)
{
var ctl = document. getElementById(id);
if(ctl)
{
return ctl.options[ctl.selectedIndex].value;
}
}
//Get the text selected by the drop-down box
function GetDDLSelectedText(id)
{
var ctl = document.getElementById(id);
if(ctl)
{
return ctl.options[ctl.selectedIndex].text ;
}
}