How to create a static variable at client side

Actually we cant create a static variable at client side. But we can keep the value even after page postback using Hidden field control.

First we need to create a hidden control and need to set ClientIDMode as "Static"

Ex: <asp:HiddenField ID="hndControl" ClientIDMode="Static" runat="server" />

After that we need to assign the value to that hidden field.

document.getElementById('<%= hndControl.ClientID %>').value = "Static";

Here after we can use that value until we change hidden field value.

How to avoid alphabets and special character from text box using javascript

Use the following code OnKeyPress Event in your text box:

<asp:TextBox ID="txtNumber" runat="server" OnKeyPress="return IsNumeric(event);"></asp:TextBox>


function IsNumeric(e) {
    var keyCode = e.which ? e.which : e.keyCode
    var ret = ((keyCode >= 48 && keyCode <= 57) || specialKeys.indexOf(keyCode) != -1);
    document.getElementById("error").style.display = ret ? "none" : "inline";
    //TestOnTextChange();
    return ret;
}

Disable Copy, Cut and Paste options in text box

Include the following options in your text box:

onpaste="return false"
oncut="return false"
oncopy="return false"

it will avoid the cut, copy and paste options from your text box