How to prevent html/JavaScript code modification

Question

I would like to know if there is a way to prevent an html page with jQuery or javascript to be modified by the user to change its behavior.

A user can modify it using tools such as FireBug or the Google Chrome developer bar to hide or show divs, add event listeners to page elements and so on.

I've seen some web pages showing a blocking div when the page is loaded and a pop-up telling to answer some question. If you answer it, the div hides and you can see the page normally. But if you try to hide the blocking div using FireBug, the page reloads and there is no way to see the page correctly if you don't ansewer the question asked in the pop-up.

I want to know how could I prevent user from doing such things.

Thanks a lot.

Answer 1

It is not possible (which is a very good thing).

Answer 2

To defeat the method described in the question:

• You can use the keyboard shortcuts to the console/tools (Ctrl+Shift+I in Chrome)
• You can use the resource/net panel to see the source
• You can see it at any other level, e.g. Fiddler
• You can use a bookmarklet for easier access

No, you can't prevent people seeing or modifying your source/script if they want to...the ones you most want to prevent are the most able to circumvent any deterrent (and that's all anything you do is, a deterrent, not a stop) you put in place.