Category: ASP Classic

How to make your server-side javascript code private in IIS

You learned that you can use Server-Side Javascript mixed in our ASP Classic VBScript application.

Next, you want to create tons of javascript files, and mix them with your old ASP. You can name them “.asp”, or “.inc”, like you did with your old VBScript files.  But, what about using intellisense in a standard editor from these extensions?

The best way to use intellisense in your favorite editor, like Visual Studio Code or anything else, is to name these files with the .js extension.

But, there’s a security issue.  If you name these files like that, they should be returned to your client in plain text if called from a web browser.  You don’t want your server-side code to be exposed through IIS.

What you need to do, is just put all these files in a specific folder, in which you will disable all IIS handlers, by using the following steps.

  1. In your application root, create a folder called private.
  2. In that folder, create a web.config file, and add this content:
<system.webServer>
  <handlers>
    <clear />
  </handlers>
</system.webServer>

You can now add all your server-side JS in that folder, and they will private to your ASP code.

If you call that js file in the browser, you will get a 404:

From your ASP page in the root, include them like this:

<script runat="server" language="javascript" src="private/code.js"></script>

That’s all! Happy Coding.

How to use Try Catch in ASP Classic

The worst part of Classic ASP in VBScript is Error Handling.

You need to type “on error resume next”, then, check, on every line, check if the previous one generates an error using [If Err.Number <> 0 then …]. That’s a real pain.

When you need solid error handling inside an ASP – VBScript sub or function, there’s a very simple method you can apply.

Just turn your existing error-handling-needed function into JavaScript, and use Try-Catch!
What? Javascript in ASP Classic?
Yes you can! It’s called JScript, it’s ECMAScript 3 compatible, and it just works.

Also, it’s totally compatible with your existing VBScript application, that will be able to call that JS method without any issue.  Even all your application VBScript variables will be shared between VB and JS.

Sample:
100% VBScript file:

<%
function fct1
	fct1 = true
	on error resume next
	' do something that can crash
	dim i : i = 1
	i = i / 0
	if err.number <> 0 then
		fct1 = false
		response.write err.number & "<br>"
		response.write err.description & "<br>"
	end if
	on error goto 0
end function

sub sub1
	dim value : value = fct1()
	response.write "result: " & value
end sub

call sub1()
%>

Now, the same, using mixed VBScript/ Javascript

<script runat="server" language="javascript"> 
function fct1(){
	try{
		// do something that can crash 
		var i = 1;
		i = parseINT(i); // <- typo
		return true;
	}
	catch(e){
		Response.Write(e.message);
		return false;
	}
}
</script>
<%
sub sub1
	dim value : value = fct1()
	response.write value
end sub

call sub1()
%>

Now, go and start converting your Classic ASP functions in JavaScript!
Just, watch out as JScript is case sensitive, VBScript is not.
vb: response.write "txt"
js: Response.Write("txt");

 

How to mix Classic ASP and Server-Side Javascript

Sometimes I need to fix some old Classic ASP applications or add small new features to them.

Because I do Javascript or C# every day for new apps, it hurts to get back to VBScript for these old apps!

That’s why I try to do these using Server-Side Javascript instead.  But wait, how can I mix NodeJS and VBScript?  The answer is, you can’t.  But, there was Server-Side JS before NodeJS exists!

Now, look at this.

You have a ASP Classic site like this:

<body>
<% dim product : product = "apple"
response.write product %>
...

And you need to create a new function to get the product name.

But, you don’t want to do it in VBScript, because you prefer JavaScript.

All you need to do is to create an “include” file, in pure javascript, like this:

includeJS.inc:

function getProduct(){
	var product = "banana";
	return product;
}

And, add it to your existing ASP file:

<script runat="server" language="javascript" src="includeJS.js" ></script>

Finally, you can fix your existing code like this:

<% dim product : product = getProduct()
response.write product %>

Yes, the VB code can call JS function directly.
Also, your JS code can also use already existing VBScript functions and variables.

(edit 2020-12-23) I just added a working sample for this, that you can download, including web.config “urlrewrite” to keep your js-code hidden from browser direct call.

IIS can run Server-Side Javascript since 1997

When I read articles about NodeJS, they almost all consider NodeJS like if Ryan Dahl invented Server-Side Javascript.

But, did you know that, in IIS 3.0 on Windows NT 4.0, it was possible to run server-side javascript?

On May 15, 1997, Microsoft released the Service Pack 3 of Windows NT4, introducing Active Server Page technology (ASP).

Classic ASP was built to run Active Script.  VBScript AND JScript are the first Active Script languages developped, and were included in all versions of Windows since 95.  And, that “Jscript”, can be used to run server-side javascript.

Wait, JScript is not JavaScript?  Yes it is. Just another name.  FireFox 1.0 run something named JavaScript 1.5, and IE6 run JScript 5.0  And, both were, in fact, ECMAScript 3.0. (more info)

That said, it means that if you still need to work with Classic ASP application, to maintain old software that can’t be rewritten, you can write some JavaScript to do that.  And, it is totally compatible with existing VBScript app!

Now, look at this sample of a 100% server-side javascript in an classic ASP file.

I’ll show you, in another article, how you can add some javascript in your existing Classic ASP / VBscript application.