How to enable clipboard in firefox?

As we know to enable clipboard in Firefox user hav开发者_高级运维e to type 'about:config' in address bar and set 'signed.applets.codebase_principal_support' true. How make this is in Javascript? (user able to agree or disagree)

You can not.

Firefox doesn't even trust you in there (the here be dragons dialogue/warning).

However, you can use a small Flash video to enable copy to the clipboard handling in Firefox.

There is a W3C proposal for a Clipboard API and Mozilla is currently working on implementing it. However, this work is still in early stages and it is unclear when it is supposed to be done.

You can't. Firefox doesn't give web developers a chance to present the user with a simple dialog to reduce their security settings.