Change window.location prototype to disable certain redirects?

Question

I'm trying to selectively disable window.location, using Greasemonkey, at the start of the document.

I don't want to fully disable javascript, just disable some redirects done with javascript. They look like this:

window.location = "unwanted url";

Rancho

Why do you want to do this? – Mallissa

How are the redirects being done, exactly? There's at least 5 possible ways. – Hanes

@brock, window.location=urltoredirect; (at)crazy I want to stop some redirections without disabling javascript... – Rancho

Answer 1

You can't change the window.location prototype, because this a "native property" of window and it is not configurable.

On Firefox (Greasemonkey), if you try to override this then you will get errors like:

TypeError: can't redefine non-configurable property 'location'

and

Error: Permission denied to shadow native property

...depending on how you attempt it. Other browsers give similar errors.

---

To block this kind of relocation, you need to interfere with the page's javascript on a case-by-case basis.

See "Stop execution of Javascript function (client side) or tweak it" for a general approach that works in Firefox. Although it may be much easier, depending on your target page's exact code.

Hanes

alright, this works when it's <script>content</script>, but what about <script src="url"></script>? is there a way to stop it too? – Rancho

Yes, checkForBadJavascripts() has a mode that does that. Or, you could just use Adblock to block that exact script URL. – Hanes

Answer 2

I don't think it's possible.

• You can't overwrite properties or methods on window.location (fails silently)
• you can't redefine its prototype with location.__proto__ = Something.prototype
• location.constructor.prototype is basically Object.prototype
• the constructor doesn't really do anything (like create the attributes or methods)
• __definesetter__ fails silently
• Object.defineProperty gives an error like, TypeError: Cannot redefine property: href
• delete window.location and delete window.location.href don't do anything

I'm out of ideas...

Typecast

This sucks! Seems that nothing has changed in 2016 :-( – Valadez

Answer 3

quite too late but you can do it simply without removing the whole script with Object.prototype.watch:

window.watch('location', function( attr ,_ , target){
    if(target.indexOf('unwanted url') !== -1)return '#';
});

Georgenegeorges

"TypeError: can't watch objects of non-native class Proxy" – Kamp

cannot watch window or other paths to location – Sanasanabria

This function is implemented only in Gecko as the op asked.And there was a bug in Firefox 23 to 27 that causes this type error but it's now fixed. – Georgenegeorges

This does not work in FF 49, if it ever did at all. JS redirects still function with no interference. – Hanes