tax calculation

Question

javascript:

function taxCalc()
{
var _txt1 = document.getElementById('<%= txtPremamnt.ClientID %>');
var _txt2 = document.getElementById('<%= txtSrvtax.ClientID %>');
var _txt3 = document.getElementById('<%= txtTotamnt.ClientID %>');
var t1=0, t2=0;

if(_txt1.value != "") t1=_txt1.value;
if(_txt2.value != "") t2=_txt2.value;

_txt3.value = parseInt(t1) + (parseInt(t1) * (parseInt(t2) / 100));
}

<asp:TextBox ID="txtPremamnt" runat="server" onkeypress="taxCalc();" class="form-control " placeholder="Pre. Amt"></asp:TextBox>

<asp:TextBox ID="txtSrvtax" runat="server" placeholder="Srv. Tax" class="form-control "></asp:TextBox>

<asp:TextBox ID="txtTotamnt" runat="server" placeholder="Tot. Amt" class="form-control "></asp:TextBox>

OUTPUT:

 

Pre. Amt:1000 

Tax: 10

Total:110

 

when I changed

 

Pre. Amt:1000

Tax: 10

Total:1100

 

Please check this