show hide javascript

Here is sample how to show hide, control in asp.net/javascript
let say we have ddBerechnung control and we have to hide controls when this dropdown has value 'identisch'

server side will have this :

         
protected override void OnPreRender(EventArgs e)
{
	ddBerechnung.Attributes.Add("onChange", "ShowHidePercentField(this)");
}

and aspx will have this javascript:

         
function ShowHidePercentField(cb){
                var selIdx = cb.selectedIndex;
                var newSel = cb.options[selIdx].text;
                var textBox=document.getElementById('<%=txtBerechnung.ClientID%>');
                var Runden= document.getElementById('<%=ddRunden.ClientID%>');
                var RundenSpan= document.getElementById('RundenSpan');


                if (trim(newSel)=='identisch'){  ///
                        textBox.style.display="none";
                        Runden.style.display="none";
                        RundenSpan.style.display="none";

                }else{
                        textBox.style.display="";
                        Runden.style.display="";
                        RundenSpan.style.display="";

                }

        }

///.... at the end of control
<script language='javascript'>
        var elem=document.getElementById('<%=ddBerechnung.ClientID%>')
        ShowHidePercentField(elem);
</script>

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