Question

How can i assign value to javasctipt variable from code-behind (C#)?

<script type="text/javascript">
String.prototype.trim = function () { return this.replace(/^\s+|\s+$/, ''); };
function ConstantByCode(_Obj, _Div) {
    var pl = new SOAPClientParameters();
    _Obj.value = _Obj.value.trim();
    pl.add("Code", _Obj.value);
    pl.add("Group", _Obj.Grp);
    alert(_Obj.Grp);
    var _Value = SOAPClient.invoke("ConstantWS.asmx", "GetConstantByCode", pl, false, CallBackEvent);
    if (_Value == null || _Obj.value == "" || _Obj.value == null || IsNumeric(_Obj.value) == false) {
        _Obj.value = "";
        _Div.innerHTML = "";
    }
    else {
        _Div.innerHTML = _Value;
    }
}


function CallBackEvent(r) {

}
function IsNumeric(input) {
    return (input - 0) == input && input.length > 0;
}

BehindCode

 txtCode.Attributes.Add("Grp", Me.ConstValue)
    txtCode.Attributes.Add("onchange", "ConstantByCode(this," & DivTitle.ClientID & ");")
    txtCode.Attributes.Add("onkeyup", "ConstantByCode(this," & DivTitle.ClientID & ");")

_obj.Grp has now value.
alert said : undefined

Answer 1

I see that you want to retrieve value of Grp that is a custom attribute. You need to use getAttribute function – so instead of _Obj.Grp, you need to use _Obj.getAttribute("Grp").

Also, I see that you are not enclosing client id in quotes from ode-behind. So instead of

txtCode.Attributes.Add("onchange", "ConstantByCode(this," & DivTitle.ClientID & ");")

you need to say

txtCode.Attributes.Add("onchange", "ConstantByCode(this,'" & DivTitle.ClientID & "');")

Note the single quote(‘) around the client id.

Further, ConstantByCode js function appears to be taking div element. Hence, you need to add line to it for converting from client id to actual DOM. i.e.

function ConstantByCode(_Obj, _Div) {
   _Div = document.getElementById(_Div);
   .... // rest of the code