Is there any way to prevent override/overwrite of functions/variables in singleton instance?

Question

Consider this pseudo code:

(function(window){
   var options = { /*where everything goes */ };

   var instance = (functio         


        

Answer 1

If anyone ever wanted to manipulate this code (a malicious user for example), he would rewrite the is_allowed function with his own

He could rewrite your whole javascript code or not even use a browser but simulate a "browser-less" request to your server.

Is there ANY way that it work in old browsers (namely IE6-8) without too much hassle?

No. Anything you globally expose can be altered by the user, it is up to the browsers restrict the javascript: behavior to avoid users from being fooled to access pre-crafted links. Firefox recently have made some kind of change to the javascript URL protocol.

As said on this article: http://survey-remover.com/blog/javascript-protocol-dangers/

As of Chrome v13, Firefox v6 and IE 9, the browser developers have taken notice to the dangers of the "javascript:" protocol and have subsequently disallowed code ... In the case of Chrome and IE, the "javascript:" substring is stripped when the code is pasted, whereas Firefox no longer executes the script within the scope of the active page.

So...

If it's impossible, then I'll just shrug and move on.

You should.