How do I put javascript programmatically into <head> block?

StackOverflow https://stackoverflow.com/questions/20083905

Question

I need to put some javascript absolutely in the <head> block of the page -- it must execute before the rest of the page because a possible outcome of the script is to redirect to a different page.

However, when I use RegisterClientScriptInclude (to put some jQuery in there) and RegisterClientScriptBlock for my code which uses the jQuery, it puts it near the top of the <body> block, and it does not execute. I can't see a way to programmatically put this javascript into the <head> block -- it must be programmatically because sometimes I don't want it there, and sometimes I do.

I've tried to see if I can directly reference Content1, the ID of the asp:Content element corresponding to the <head> block, but no go.

Just in case anyone thinks that RegisterStartupScript might work: it doesn't. It puts it lower in the <body> block than everything else. Oddly enough.

Want some code? Here:

Type csType = this.GetType();
ClientScriptManager clientScript = Page.ClientScript;

if (!clientScript.IsClientScriptIncludeRegistered(jqueryScriptName))
{
    clientScript.RegisterClientScriptInclude(jqueryScriptName, "~/Scripts/jquery-1.7.1.min.js");
}

if (!clientScript.IsClientScriptBlockRegistered(citrixDetectorScriptName))
{
    clientScript.RegisterClientScriptBlock(csType, citrixDetectorScriptName, citrixDetectorScriptText, true);
}

By popular demand, how I detect the ActiveX component. This is JScript.

try {
    var icaObj = new ActiveXObject("Citrix.ICAClient");

    var CitrixVersion = icaObj.ClientVersion.split(".");
    var MajorMinorVersion = CitrixVersion[0] + "." + CitrixVersion[1];
    if (MajorMinorVersion == "11.0") {
        // Citrix is OK
    }
    else {
        window.navigate("WrongCitrix.aspx?Citrix=" + MajorMinorVersion);
    }
}
catch (e) {

    window.navigate("NoCitrix.aspx");
}

If the ActiveX component is not present, then redirection is a page that tells the user they need to install it. If the ActiveX component is any other version than 11.0, then the redirect is to a page that explains this and how to deal with the situation (backrevving for example).

An prior check during page load checks to make sure they have Internet Explorer v4 thru v9, because any other version will not work with the product (and IE10+ will crash if it even tries to load v11.0 of the ActiveX component).

Was it helpful?

Solution

If I understand your question, you can insert PlaceHolder control wherever you want inside the page.

<%@ Page Language="C#" AutoEventWireup="True" 
   CodeBehind="Default.aspx.cs" Inherits="WebApplicationTelerik.Default" %>
<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <script type="text/javascript" 
    src="//ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
    <asp:PlaceHolder runat="server" ID="PlaceHolder1"></asp:PlaceHolder>
</head>
<body>
    <form id="form1" runat="server">
    </form>
</body>
</html>

protected void Page_Load(object sender, EventArgs e)
{
    PlaceHolder1.Controls.Add(new LiteralControl(
       "<script type=\"text/javascript\"> alert('here'); </script>"));
}

OTHER TIPS

document.GetElementsByTagName("head")[0].appendChild( newScriptNode );

or jQuery

$("head")[0].append( newScriptNode );

If you really must insert JavaScript into the head tag, you can just make it an ASP.NET control and insert a control into it's child collection.

E.g. In the ASPX file:

<head runat="server" id="header">...</head>

In the code behind:

header.Controls.Add(new Literal("<script type='text/javascript'>...</script>"));

Although I do think you need to think about your process, it would be more efficient to redirect the user in the back-end before the page is rendered.

Oh and RegisterStartupScript correctly places your JavaScript after your html for increased load performance.

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